spirit lake feasibility study (pdf)
TRANSCRIPT
Revised Feasibility Study
Former Duluth Works and Spirit Lake Sediment Site
Prepared for Great Lakes Legacy Act Partnership between United States Steel Corporation, and Unites States, Environmental Protection Agency, Great Lakes National Program Office, and Minnesota Pollution Control Agency
In Consultation with EA Engineering, Science, and Technology, Inc.
Prepared by Barr Engineering Company AECOM (formerly URS Corporation)
July 2015
Revised Feasibility Study
Former Duluth Works and Spirit Lake Sediment Site
Prepared for Great Lakes Legacy Act Partnership between United States Steel Corporation, and Unites States, Environmental Protection Agency, Great Lakes National Program Office, and Minnesota Pollution Control Agency
In Consultation with EA Engineering, Science, and Technology, Inc.
Prepared by Barr Engineering Company AECOM (formerly URS Corporation)
July 2015
Published by: Barr Engineering Company 325 S. Lake Avenue, Suite 700 Duluth, MN 55802-2323 Phone: 218.529.8200
Revised Feasibility Study Former Duluth Works and Spirit Lake Sediment Site
July 2015
Contents 1.0 Introduction ........................................................................................................................................................................... 1
1.1 Purpose and Organization of Report...................................................................................................................... 1
1.2 Site Background .............................................................................................................................................................. 2
1.2.1 Site Location and Description .............................................................................................................................. 2
1.2.2 Early Land Uses........................................................................................................................................................... 2
1.2.3 Site Operational History ......................................................................................................................................... 3
1.2.4 Description of Subject Study Areas.................................................................................................................... 3
2.0 Conceptual Site Models .................................................................................................................................................... 6
2.1 Hydrologic and Geologic Setting ............................................................................................................................. 6
2.1.1 Regional Hydrology.................................................................................................................................................. 6
2.1.2 Regional Geology ...................................................................................................................................................... 6
2.1.3 Site-Specific Geology............................................................................................................................................... 7
2.2 Former Duluth Works Operations Area Conceptual Site Models................................................................7
2.2.1 Former Operations Area Hydrogeology...........................................................................................................8
2.2.2 Former Operations Area Hydrology .................................................................................................................. 8
2.2.3 Description of Former Operations Area Conceptual Site Models..........................................................9
2.3 Estuary Conceptual Site Models .............................................................................................................................10
2.3.1 Estuary Hydrology, Geomorphology, and Hydrodynamics ....................................................................11
2.3.2 Estuary Hydrogeology ...........................................................................................................................................13
2.3.3 Description of Estuary Site Models ..................................................................................................................14
3.0 Project Goals........................................................................................................................................................................17
3.1 Vision for Success .........................................................................................................................................................17
3.2 Overview of Remedial Action Objectives (RAOs) .............................................................................................17
3.3 Former Operations Area Site Remedial Action Considerations .................................................................18
3.3.1 Protect Human Health and the Environment...............................................................................................18
3.3.2 Prevent Migration and Transport of COIs and Maintain Surface Water Quality............................21
3.3.3 Preserve Areas for Economic Development .................................................................................................22
3.3.4 Improve Habitat (Betterment) ............................................................................................................................22
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3.4 Estuary Remedial Action Considerations.............................................................................................................22
3.4.1 Protection of Human Health and the Environment ...................................................................................23
3.4.2 Reduction of Beneficial Use Impairments for the St. Louis River Area of Concern.......................24
3.4.3 Improve Habitat (betterment) ............................................................................................................................25
3.5 Other Project Considerations...................................................................................................................................25
3.5.1 Consideration of Cultural and Recreational Values ...................................................................................26
3.5.2 Consideration of Green and Sustainable Principles...................................................................................26
3.5.3 Consistency with EPA Sediment Management Principles .......................................................................27
3.5.4 Compliance with Oversight and Environmental Permitting Requirements .....................................27
3.5.5 GLLA Scheduling Considerations ......................................................................................................................28
4.0 Technology Screening .....................................................................................................................................................29
4.1 Technology Identification and Screening Process...........................................................................................29
4.2 Sediment Technologies ..............................................................................................................................................30
4.2.1 Institutional Controls..............................................................................................................................................30
4.2.2 Natural Recovery .....................................................................................................................................................31
4.2.3 Capping .......................................................................................................................................................................33
4.2.4 Excavation and Removal.......................................................................................................................................35
4.2.5 Sediment Containment and Disposal..............................................................................................................39
4.2.6 In-Situ Treatment ....................................................................................................................................................42
4.3 Water Management Technologies ........................................................................................................................44
4.3.1 Surface Water Engineering ..................................................................................................................................44
4.3.2 Water Management ...............................................................................................................................................46
5.0 Alternatives Evaluation ....................................................................................................................................................48
5.1 Development of Alternatives ...................................................................................................................................48
5.1.1 Review and Input on Alternatives Development ........................................................................................48
5.2 Common Remedy Elements .....................................................................................................................................49
5.2.1 Institutional Controls..............................................................................................................................................49
5.2.2 Natural Recovery .....................................................................................................................................................49
5.2.3 ENR Thin Cover ........................................................................................................................................................49
5.2.4 Remedial Capping...................................................................................................................................................49
5.2.5 Removal to a Set Elevation and Cap Placement .........................................................................................50
5.2.6 Removal to PRGs .....................................................................................................................................................51
5.2.7 Dredge Residual Cover..........................................................................................................................................51
5.2.8 CDF ................................................................................................................................................................................51
5.2.9 Former Operations Area (Upland) CDF...........................................................................................................51
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5.2.10 Storm Water Conveyance – Unnamed Creek...............................................................................................51
5.2.11 Storm Water Conveyance – Wire Mill Pond and Unnamed Pond .......................................................52
5.2.12 Surface Water Quality............................................................................................................................................52
5.2.13 Lead-Impacted Soil .................................................................................................................................................53
5.3 Common Habitat Elements.......................................................................................................................................53
5.3.1 Open Water Bay.......................................................................................................................................................53
5.3.2 Shallow Sheltered Bay ...........................................................................................................................................53
5.3.3 Other Habitat/Recreational Elements..............................................................................................................53
5.4 Assembled Alternatives for Screening-Level Evaluation ...............................................................................53
5.4.1 Alternative 1 – Natural Recovery.......................................................................................................................54
5.4.2 Alternative 2 – Remedial Capping ....................................................................................................................54
5.4.3 Alternative 3 – Delta/Estuary CDF (Confined Disposal Facility) ............................................................54
5.4.4 Alternative 4 – CDF on OU-M Delta (within Shoreline)............................................................................55
5.4.5 Alternative 5 – CDF with Open Water Bay.....................................................................................................55
5.4.6 Alternative 6 – Shallow Sheltered Bay with CDF .........................................................................................56
5.4.7 Alternative 7 – Shallow Sheltered Bay and Delta Cap Area with Upland CDFs ..............................57
5.4.8 Alternative 8 – Shallow Sheltered Bay with Delta Sediment CDF and Former Operations Area CDFs ..............................................................................................................................................................................58
5.4.9 Alternative 9 – Delta Cover and Upland CDFs .............................................................................................58
5.4.10 Alternative 10 – Targeted Removal with Coke Plant Area CDF.............................................................59
5.4.11 Alternative 11 – Removal with Large Coke Plant Area CDF....................................................................60
5.4.12 Alternative 12 – Open Water Bay with Upland CDFs ................................................................................60
5.5 Screening-Level Evaluation of Alternatives ........................................................................................................61
5.5.1 Alternatives Retained for Detailed Evaluation .............................................................................................62
5.6 Detailed Evaluation of Retained Alternatives ....................................................................................................63
5.7 Recommended Alternative .......................................................................................................................................64
6.0 Recommendations and Path Forward .......................................................................................................................65
6.1 Recommended Project Alternative ........................................................................................................................65
6.2 Path Forward...................................................................................................................................................................69
6.2.1 Pre-Implementation Activities............................................................................................................................69
6.2.2 Project Implementation ........................................................................................................................................70
7.0 References ............................................................................................................................................................................71
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List of Tables
Table 3-1 Terrestrial Criteria By Anticipated Future Land Use Table 3-2 Former Operations Area Baseline Ecological Risk Assessment Table 3-3 Extent of Impacts Table 3-4 List of Chemicals of Interest (COIs) Table 3-5 Former Operations Area Stormwater Conveyance Goals Table 3-6 Preliminary Remediation Goals for Sediment Table 3-7 Potential Receptors Driving Habitat Zone Thickness Table 4-1 Soil and Sediment Technology Screening Ranking Table 4-2 Water Management Technology Screening Ranking Table 5-1 Quantities Summary Table 5-2 Screening Level Evaluation of Alternatives Table 5-3 Evaluation Criteria Table 5-4 Principles for Managing Contaminated Sediment Risks Table 5-5 Detailed Analysis of Alternatives Summary – Alternative 4 Table 5-6 Detailed Analysis of Alternatives Summary – Alternative 6 Table 5-7 Detailed Analysis of Alternatives Summary – Alternative 7 Table 5-8 Detailed Analysis of Alternatives Summary – Alternative 8 Table 5-9 Detailed Analysis of Alternatives Summary – Alternative 12 Table 5-10 Alternatives Comparison Table 5-11 Cost Estimate Summary
List of Figures
Figure 1-1 Site Location Figure 1-2 Site Layout Figure 2-1 Conceptual Model CDA to OU-M Figure 2-2 Conceptual Model OU-P to OU-Q Figure 2-3 Groundwater Contours Fourth Quarter 2014 Figure 2-4 Upstream Watersheds Figure 2-5 Depth to Native Material (Former Operations Area) Figure 2-6 Wire Mill Pond Delta Conceptual Model Figure 2-7 Upper Wire Mill Conceptual Model Figure 2-8 Unnamed Creek Delta Conceptual Model Figure 2-9 Post-Industrial Sediment Cover Thickness- Estuary Area Figure 2-10 Thickness of Sediment that Exceeds PRGs – Estuary Area Figure 3-1 Extent of Impacted Media Figure 5-1 Alternative 1 – Natural Recovery Figure 5-2 Alternative 2 – Remedial Capping
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Figure 5-3 Alternative 3 – Delta/Estuary CDF Figure 5-4 Alternative 4 – CDF on OU-M Delta (Within Shoreline) Figure 5-5 Alternative 5 – CDF with Open Water Bay Figure 5-6 Alternative 6 – Shallow Sheltered Bay with CDF Figure 5-7 Alternative 7 – Shallow Sheltered By and Delta Cap Area With Upland CDFs Figure 5-8 Alternative 8 – Shallow Sheltered Bay with Delta Sediment CDF and Upland CDFs Figure 5-9 Alternative 9 – Delta Cover and Upland CDFs Figure 5-10 Alternative 10 – Targeted Removal with Coke Plant Area CDF Figure 5-11 Alternative 11 – Removal with Large Coke Plant Area CDF Figure 5-12 Alternative 12 – Open Water Bay with Upland CDFs
List of Appendices
Appendix A Summary of Administrative History Appendix B Upland Surface Water Technical Memorandum Appendix C Upland Wetland Delineation Report Appendix D Summary of Hydrodynamic, Sediment Transport, and Wave Modeling Appendix E Estuary Supplemental Investigation Report & Updated Ice Evaluation Appendix F Groundwater/Surface Water Seepage Meter Sampling and Analysis Results Appendix G Potential Permitting Requirements Appendix H ARARs Appendix I Schematic Diagrams of Remedy Elements
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1.0 Introduction 1.1 Purpose and Organization of Report This revised Feasibility Study (FS), prepared on behalf of United States Steel Corporation (U. S. Steel) and the, Great Lakes National Program Office (GLNPO) of Region V, U. S. Environmental Protection Agency (USEPA), presents the results of the FS work for the former U. S. Steel Duluth Works sediment site areas and the U. S. Steel Spirit Lake sediment site in the St. Louis River, Duluth, Minnesota. Figure 1-1 shows the Site location, which includes areas of the U. S. Steel Duluth Works former operations area containing sediment and a portion of the western side of Spirit Lake, within the Saint Louis River in western Duluth, Minnesota. The former operations area sediment site (Duluth Works Site) and the estuary sediment site (Estuary Site) areas evaluated in this FS are shown on Figure 1-2 and referred to collectively as the Site in this FS.
The purpose of the FS is to identify Project options that may be feasible for addressing potential risks to human health and the environment posed by impacts present at both the Duluth Works Site and the Estuary Site. The work conducted for the Estuary portion of the Site has been conducted on behalf of U. S. Steel and the USEPA GLNPO under a Great Lakes Legacy Act (GLLA) Project agreement (Figure 1-2). The work for the Duluth Works Site has been completed by U. S. Steel alone in accordance with Section V of the March 26, 1985 Response Order by Consent (Consent Order) issued by the Minnesota Pollution Control Agency (MPCA) (Figure 1-2) (MPCA, 1985). The evaluation of sediment activities at both the Duluth Works Site and the Estuary Site have been combined in this FS to help identify areas where complimentary actions, for example consolidated on-site disposal, may provide synergies and ultimately a better remedy.
This FS is divided into seven sections:
x Section 1 Introduction provides an introduction and purpose, describes the report organization, and provides a background and overview of the Site.
x Section 2 Conceptual Site Models describes the conceptual site models (CSM) for the Site, including the environmental setting, the nature and extent of potential environmental impacts associated with the Site, and the potential fate and transport of the constituents of interest (COI). This section also contains a summary of the baseline risk assessment.
x Section 3 Project Goals defines the Project goals of protecting human health and the environment in terms of site-specific and location-specific targets for sediment quality at the conclusion of a Project that is developed from this FS process.
x Section 4 Technology Screening considers potential technologies that could be used to complete a Project for the Site and contains a summary of the technology screening process. This section also contains a summary of the treatability studies completed for the purpose of evaluating technologies.
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x Section 5 Alternatives Evaluation presents the development of potential Projects for the Site by combining technologies that have passed the screening process and applying them to specific areas of the Duluth Works or the Estuary Sites. This section also includes an evaluation of alternative Project scenarios and describes the Site sediment management goals and Applicable or Relevant and Appropriate Requirements (ARARs).
x Section 6 Recommendations and Path Forward contains the selection of a preferred alternative. This section also contains recommendations, discusses the Project design process and permitting, and presents a schedule for implementation of the preferred alternative.
x Section 7 References
1.2 Site Background 1.2.1 Site Location and Description The Site is located in Sections 34 and 35, T49N, R15W, and Sections 2 and 3, T48N, R15W, in the southern part of the City of Duluth in St. Louis County, Minnesota (United States Geological Survey [USGS] 1954, 1993) (Figure 1-1). The Site is adjacent to the St. Louis River, which discharges into Lake Superior approximately eight miles downstream of the Site. The Estuary portion of the Site is located in an open reach of the St. Louis River referred to as Spirit Lake. The Site layout and relation to the former U. S. Steel Duluth Works are shown on Figure 1-2. A small creek and community storm water conveyance channel, referred to as the Unnamed Creek, carries flows from 2,000 acres of upstream watershed within the City of Duluth and Midway Township. It enters through a large culvert located along the western edge, flows through the western portion of the Site and discharges to the St. Louis River. The Site is bounded by Morgan Park (a neighborhood in Duluth, MN) to the north, the St. Louis River (Spirit Lake section) to the east, the Canadian National Railway (CN) property to the west and U. S. Steel-owned former steel mill facility area to the south.
1.2.2 Early Land Uses The pre-industrial history of the lower St. Louis River estuary area is discussed in detail in the St. Louis River Citizens Action Committee Lower St. Louis River Habitat Plan document (2002). The earliest written descriptions of land uses near the Site date to the 1600s, which is when “…Europeans came to the area to explore and trade…” with the native American people who occupied the region at that time (St. Louis River Citizens Action Committee, 2002). The Fond du Lac Band of the Lake Superior Chippewa are reported to have had villages at various locations along the lower St. Louis River, including the present-day location of the Fond du Lac neighborhood of Duluth, prior to the 1800s. The Fond du Lac neighborhood is located approximately _5.5 miles upstream of the Site. The Citizens Action Committee document (2002) notes that seasonal camps were reported to have been present at Spirit Lake and nearby Indian Point (2.5 miles down-river from the Site).
Maps indicate no settlement features in the immediate Spirit Lake area when the first available map was published in 1861. An archeologist surface walk conducted on Spirit Island in November 2012 found artifacts indicating some occupation of the island; however, no observed cultural features were reported
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on the surface of the island (Duluth Archeology Center, 2013). No archeological subsurface investigations have been conducted in the area according to this report (Duluth Archeology Center, 2013). The cultural significance of Spirit Island is based on the migration history of the Chippewa, as well as the discovery of wild rice. Spirit Island is considered the sixth stopping place of the journey west, and a meeting location between groups that traveled north of the Great Lakes, and groups that traveled south of the Great Lakes (Duluth Archeology Center, 2013).
The LaPointe Treaty was signed in 1854 between the United States government and the Chippewa which opened the area to settlement (St. Louis River Citizens Action Committee, 2002). The town sites of Duluth and Superior, Wisconsin were then platted. Construction of the first railroad in the lower St Louis River area began in 1861 and was completed in 1870. Historic maps presented in Appendix J of the Remedial Investigation report (Barr, 2013a) show no mapped development in the Spirit Lake area in 1861. The railroad along the river bank was present on a map dated 1889, the next known historic map. A railroad track was also present several miles to the west of the river in 1889, which appears to be the location of the higher elevation Duluth Winnipeg Pacific Railroad (Northern Pacific Railroad). No other development is noted around Spirit Lake on the 1889 map. By 1902, another railroad track was present less than one mile east of the Northern Pacific Railroad, near the current location of Grand Avenue. This newer railroad is listed as the Great Northern Railroad on the 1909 map. The town site of Smithville is on the 1902 map, but, no development, except for the railroad built by 1889 along the river bank, is shown around Spirit Lake in 1902. The property on the Minnesota side of Spirit Lake is titled Spirit Lake Park on the 1902 map. The U. S. Steel property area is labeled as Minnesota Steel Co. Location on a 1909 map, and the steel plant facilities and railroads associated with the plant operations are present on a 1917 map. No additional railroad development along the river bank was noted beyond the tracks built by 1889.
1.2.3 Site Operational History U. S. Steel built the former steelmaking facility beginning in 1907, with operation beginning in 1915. The facility consisted of a fully integrated steel manufacturing plant including coke production, iron and steel making, casting, primary rolling and roughing, hot and cold finishing, and galvanizing. The majority of the operation was closed in 1979. The approximate former operational area is shown on Figure 1-2.
By the end of 1988, most of the buildings that made up the operation had been demolished and by 1999, the Wire Mill and several smaller buildings used for storage were also removed. Currently, the only structure remaining is a small shed near the Site entrance; this and a few concrete pads and roads are the only remaining surficial features.
The Site is part of a larger Superfund site referred to as the former Duluth Works Superfund site. The Superfund site is overseen by the MPCA under a Consent Order (MPCA, 1985). An administrative record synopsis is provided in Appendix A.
1.2.4 Description of Subject Study Areas The primary focus of this FS will be several Study Areas (SAs) within the Estuary and adjoining portions of the Site (Figure 1-2). The Estuary portion is comprised of two main SAs along the western shore of Spirit
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Lake which closely mirror Operable Units N and R (Figure 1-2). Not all of the Former Duluth Works Superfund sites Operable Units (OUs) are evaluated in this FS; only the following five (5) Former Duluth Works Site OUs, two (2) Estuary Site OUs, and four (4) Former Duluth Works Site SAs are evaluated.
The Former Duluth Works SAs and OUs are described as follows:
Tar Impacted Soil (SAs – T-10 and T-11) – Areas of hardened tar-like material/oil on the surface and tar-like material/oil seeps were identified across the Site during 2008 site reconnaissance. Further response actions at two tar/oil seeps, T-10 and T-11, located in the Unnamed Creek valley near the Coke Plant, will be incorporated into the FS based on recommendations presented in the Supplemental Five Year Review Investigation Report (URS, 2011).
Non-native Material in the Settling Basin (OU-I) – The non-native material is present in the Coke Plant Settling Basin immediately upstream of the basin outlet control structure. This area is approximately 1,400 feet long and up to 330 feet wide, covering approximately 6.3 acres.
Tar and Tar-Impacted Soil in the Coke Plant Settling Basin (SA – Tar between I & J) – This area of tar-like material and tar-like impacted sediment in the Coke Plant Settling Basin is located between, but was not included as part of OU-I or OU-J. The area is approximately 375 feet long by 270 feet wide and encompasses about 1.2 acres. Periodic day-lighting of tar-like material has been observed in the pond area within Tar Between I & J. U. S. Steel has installed absorbent booms to contain the tar-like material and has conducted periodic recovery of the floating tar-like material since 2007.
Stream Channel (OU-L) – The stream channel located between the Coke Plant Settling Basin Control Structure, near the entrance road, and the railroad tracks that parallel the St. Louis River. The stream channel is approximately 1,300 feet long and up to 350 feet wide, encompassing approximately three acres.
Delta and Stream Channel (OU-M) – This area consists of the delta adjacent to the stream channel downstream of the Coke Plant Settling Basin Control Structure, (also called the delta or stream channel area), and includes a former open water area to the west of the railroad tracks. The delta and stream channel SA is characterized by the presence of non-native material. The maximum length and width of the delta and stream channel are 2,830 feet and 1,640 feet, respectively, encompassing about 46 acres.
Wire Mill Pond (OU-P) – The Wire Mill Pond is a portion of the settling basin for process sewer discharge from the Wire Mill and stormwater runoff from a large portion of the Site. The Wire Mill Pond contains non-native material as a consequence of acting as the primary settling basin.
Following initial response actions completed in 1997, the length and width of the Wire Mill Pond area addressed in the FS is approximately 520 feet and 170 feet, respectively, covering an area of approximately 1.1 acres.
Non-native Material and Dredge Spoils in Wire Mill Settling Basin (OU-Q) – Non-native material was dredged to form the Wire Mill Pond Settling Basin and placed along the north and south shore of the Wire Mill Pond within the limits of the historical basin. The maximum length and
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width of Wire Mill Settling Basin dredge spoils is approximately 1,200 feet and 640 feet, respectively, covering an area of approximately 7.4 acres.
Concrete Disposal Area (SA – CDA) – The Concrete Disposal Area is an earthen embankment on the west side of the property, and east of the CN railroad tracks. This area, measuring approximately 1,000 feet long by 600 feet wide (approximately 14 acres), is devoid of vegetation and appears to be covered with light-colored concrete debris (Figure 1-2). The MPCA has referred to this material as "crushed slag"; however, based on surface reconnaissance, the material consists of mostly crushed concrete.
Unnamed Pond (SA – Unnamed Pond) – Approximately 1.8-acre pond located in the vicinity of the former plant pump station within the northeast quadrant of the Site. Abandoned “oil recovery” equipment was observed at the pond but the actual use of the equipment was never conclusively identified in historic records. Results from Former Duluth Works sediment samples collected after the 2003 Five-Year Review identified residual impacts in the sediments.
The Estuary Site SAs are generally described as follows:
Wire Mill Delta (OU-R) – is approximately 274 acres of water-covered estuary area near the discharge pond from the former Duluth Works wire mill. This study area is located on the south side of a man-made spit of land that separates the two delta areas, with a natural land barrier and wetland defining the southern boundary and the main river channel defining the eastern boundary.
Unnamed Creek Delta (OU-N) – is approximately 110 acres of water-covered estuary north of the Wire Mill Delta at the outlet of Unnamed Creek, where it empties into Spirit Lake. Located north of the spit separating the two deltas, this study area is characterized by a broad, flat delta at the mouth of the creek. Barrier islands are to the east and a dredged shipping channel extends from the main river channel on the north towards the spit on the south.
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2.0 Conceptual Site Models The development of CSMs allows data obtained during on-going investigations to be integrated in an iterative approach that increases the understanding of the physical and environmental setting of the Site and the fate and transport of COIs. This Section contains a general overview of the regional hydrologic and geologic setting, which is common to both the Former Duluth Works and Estuary Sites, along with detailed descriptions of the CSM for the Duluth Works and the Estuary Site areas. These CSMs are based on site-specific data and observations that have been collected during several investigations over multiple years. The CSMs provide a baseline for consideration of how Project alternatives could be implemented to protect human health and improve the environmental habitat of the Site.
2.1 Hydrologic and Geologic Setting 2.1.1 Regional Hydrology The Site is located within the St. Louis River watershed, which drains approximately 4,000 square miles of northeastern Minnesota and a portion of northwestern Wisconsin. The region has a typical Midwestern climate with annual average precipitation (rain) of 31 inches, and an average annual snowfall of 85 inches. The regional climate is influenced by the presence of Lake Superior, which has a moderating effect on temperature extremes near the estuary. For example, the mean annual temperature is 39.5 degrees F with a range from minus-39 degrees F to 98 degrees F near the mouth of the St. Louis River in Duluth, while the mean annual temperature in the upper portions of the St. Louis River watershed near Eveleth is 38.75 degrees F with a range from minus-46 degrees F to 103 degrees F.
Groundwater development within the region is limited, and primarily restricted to the glacial lake sands and gravels, due to the inadequate quantity of usable groundwater in the gabbro and thick silt and clay units (Lindholm et al., 1979) as described in Section 2.1.2. Additional details regarding the Site hydrology, hydrogeology, hydrodynamics and geomorphology are integrated throughout the following CSM discussions.
2.1.2 Regional Geology The geology of the watershed consists primarily of glacial deposits of varying thicknesses and composition overlying igneous and metamorphic bedrock. The primary bedrock unit is the Duluth Complex, a laterally extensive, massive, olivine and anorthositic gabbro formed at or below the ocean floor of a failed Precambrian rift-formed submarine valley. (Lindholm et al., 1979). In the St. Louis River estuary, the bedrock is overlain by 300 to 500 feet of silt and clay lake deposits, with localized saturated glacial lake sands usually less than 10 feet thick.
Quaternary glacial sedimentary deposits in the area of the Site consist of red silt and clay deposited in ancestral Glacial Lake Duluth. These silt and clay lake sediments are prevalent throughout the lower elevations in Duluth including the estuary.
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2.1.3 Site-Specific Geology The Duluth Works Site has been extensively modified and filled during industrial development and activity. Fill material present at the Site consists of gravel, cinders, slag fragments and other materials. The characteristics of the fill material vary throughout the Duluth Works Site. The native soils present beneath the fill material consist of red-brown clay underlain, and at times interbedded with a fine to medium sand (Barr, 1986). The clay unit depth varies from 2 to 48 feet (ft.) beneath the ground surface, and the thickness ranges from 2 to 32 ft. Beneath the clay unit are deposits of sand and gravel. Bedrock was not encountered during any of the investigation activities.
The Estuary Site has a variety of sediment types typical of dynamic fluvial environments: clay, silt, organic silt, sandy silt, silty sand, sand, gravel, and peat. The native sediment types are interlayered, with most layers not laterally extensive. Individual layers of a specific sediment type do not extend completely across the Estuary Site. Silt and organic silt is the predominant surficial sediment type in the estuary, except in the two deltas, which are dominated by sand and separated by a spit of land created primarily from fill. Sand is also present as the surficial sediment in portions of Spirit Lake near the main channel of the St. Louis River.
Non-native sediment classified as fill is present in locations within the estuary, including an area of cemented fill within the Unnamed Creek delta. Fill material includes sand- and gravel-sized anthropogenic materials mixed with natural sediment, metal shavings or fragments, other non-native debris, or particles such as apparent coke or coal fines (generally less than fine-sand sized), apparent mill scale, and naphthalene crystals.
Additional details related to site-specific geologic conditions are included in the Duluth Works Site area and Estuary conceptual models.
2.2 Former Duluth Works Operations Area Conceptual Site Models Two former Operations area CSMs applicable to this FS were described in detail within the Remedial Investigation Addendum (RIA) submitted by U. S. Steel to the MPCA in October 2013 (URS, 2013). The CSMs considered both terrestrial and aquatic release mechanisms, exposure pathways, migration routes, and potential receptors along the alignment of the Unnamed Creek and Wire Mill Pond drainage courses.
Separate CSM diagrams were prepared for these two areas of the former Duluth Works Operations Site:
x The Unnamed Creek, extending east from the western Site property boundary and CDA area to the OU-M delta (Figure 2-1); and
x The Wire Mill Pond, extending east from the former Site Wire Mill to the St. Louis River estuary (Figure 2-2).
New information that would materially change the former Duluth Works Site area CSMs has not been generated since the submittal of the October 2013 RIA. As such, this FS report section provides a summary of previously submitted information.
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2.2.1 Former Operations Area Hydrogeology Shallow groundwater at the Site flows primarily according to topography and the major drainage patterns. The groundwater elevation map from the RIA is presented on Figure 2-3. Groundwater east of monitoring wells MW-7 through MW-13 appears to flow in an easterly direction toward the St. Louis River. Groundwater north of monitoring well MW-7 appears to flow in a north-northeasterly direction toward the Unnamed Creek. In the area of the Wire Mill Pond groundwater generally flows toward, and discharges to, the pond. Similarly, lowland areas along the St. Louis estuary likely intercept shallow groundwater flow prior to it reaching the river. Groundwater is generally found at 27 to 31 ft. below ground surface (BGS) (UEC, 1993) in the Former Operations portions of the Site and between 0 and 4.9 ft. BGS in the lowland areas.
With the exception of the CDA, no groundwater impacts of concern are related to the SAs addressed in this FS. A general summary of the monitoring and results for the subject SAs was provided in the RIA, at the request of the MPCA, to provide context for the Former Operations Area sediment data and discussion. The reader should refer to the RIA and annual monitoring reports for additional discussion of groundwater quality at the Former Operations Site.
2.2.2 Former Operations Area Hydrology The portion of Unnamed Creek crossing the Former Operations area of the Site was identified by the U. S. Geological Survey (USGS) in a 2003 and 2004 geomorphic study of the Duluth area as the lower main stem of “U. S. Steel Creek” (Fitzpatrick, et. al., 2006). The artificial channel designation of this surface water body within the USGS study is consistent with its current use as a major storm water drainage conveyance for the City of Duluth. The majority of the base and storm flow in the Unnamed Creek originates in areas of the watershed that are up gradient of the Site (Figure 2-4). Off-site run-on generally flows from the west and northwest from multiple sub-watersheds and is conveyed by Unnamed Creek to the St. Louis River estuary. The largest of these off-site watersheds has an approximate area of 1,600 acres. This watershed has a maximum elevation of approximately 1,300 feet above mean sea level (msl) and a vertical relief of approximately 590 feet. Two smaller sub-watersheds flow onto the site from the northwest and north, respectively. The first is approximately 257 acres, with a vertical relief of approximately 500 feet and discharges to the Unnamed Creek tributary north of OU-K. The second is a Morgan Park, Minnesota residential area covering approximately 51 acres and has a vertical relief of approximately 10 feet. Storm water in this sub-watershed not captured by the City of Duluth storm sewer system is believed to enter Unnamed Creek via overland flow. Peak discharges are summarized in the Upland (Former Operations Area) Surface Water Technical Memorandum provided as Appendix B.
Wire Mill Pond has a drainage area of approximately 34 acres. This 34-acre on-site sub-watershed is located in the east central portion of the site and generally flows to the east and is conveyed by the Wire Mill Pond into the St. Louis River estuary. The sub-watershed has a vertical relief of approximately 60 feet and a low point (or outlet elevation) of approximately 601 feet msl.
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Unnamed Pond, a third Former Operations Area surface water body included within the scope of this FS, has an on-site drainage area of approximately 14 acres. Overland flow within the drainage area is to the east with a vertical relief of approximately 40 feet and a low point of approximately 607 feet msl.
Four wetland areas, ranging in size from two to 11 acres, were mapped during a wetland delineation and functional assessment effort conducted in conjunction with this FS (Appendix C). The wetlands identified in this study were aligned with the Unnamed Creek corridor, as well as the Wire Mill and Unnamed Pond areas. All of the wetlands identified in the study were considered to be significantly disturbed and have been subjected to numerous wetland type changes as land use and hydrology have been changed by direct and indirect post-industrial impacts that occurred prior to 1980 (Appendix B).
Surface water quality is addressed via ongoing monitoring and reporting. All surface water data are reported to the MPCA in separate submittals. A general summary of the monitoring and results for the subject SA’s was provided in the Remedial Investigation Addendum (RIA), at the request of the MPCA, to provide context for the Former Operations Area sediment data and discussion (URS, 2013). The reader should refer to the RIA and annual monitoring reports for additional discussion of surface water quality.
2.2.3 Description of Former Operations Area Conceptual Site Models 2.2.3.1 Unnamed Creek Conceptual Site Model Figure 2-1 shows a conceptual cross section and risk pathway diagram for the Unnamed Creek comprising the CDA, OU-I, OU-J, Tar Between I&J, OU-L, and OU-M. Past and present investigations have identified that essentially all the sediment fill above the original natural creek elevation is impacted with coke fines, manifested primarily as elevated PAH concentrations. Historically, the Unnamed Creek channel received coke fines near OU-J. The fines were subsequently transported downstream and make up a significant portion of the sediment in Unnamed Creek (OU-I) and the OU-M delta. While transport of sediment from the upper portion of the Unnamed Creek to the estuary remains a primary concern at the Site, today the OU-M delta and much of the Unnamed Creek is vegetated, which greatly reduces sediment transport.
Potential exposure pathways for the Unnamed Creek sediment include direct exposure to both ecological and potential human receptors (i.e. trespassers). Surface water quality exceedances, in the form of oil blooms in the Tar between OU-I and OU-J and detections of select metals, PAHs and elevated pH have also been noted in the Unnamed Creek corridor. However, the Unnamed Creek is difficult to access and not attractive for wading or other activities, which likely limits the potential for direct human exposure.
The Unnamed Creek is likely a groundwater discharge zone as various seeps have been observed along the shoreline of the creek. While this limits the potential for groundwater to transport COIs away from the creek, it is a potential mechanism for transport into the creek through impacted sediment within the creek-bed. As discussed above in Section 2.2.1, groundwater discharge to the Unnamed Creek is anticipated to represent a small portion of the total Unnamed Creek base flow.
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2.2.3.2 Wire Mill Pond Conceptual Site Model Figure 2-2 presents a conceptual cross section of the Wire Mill Pond (OU-P and OU-Q). This area was historically an inlet on the estuary that was filled over time. Later, dredge spoils from the Wire Mill Pond were placed along the north and south banks of the Wire Mill Pond to create much of the current topography (Figure 2-5). As part of the remediation of the Wire Mill Pond in 1997, the pond was dredged restored with a sand backfill to create a benthic ecology to help contain remaining sediments. The primary risk pathways in this area include sediment transport to the estuary and infrequent oil blooms within the pond. This pathway is currently addressed by the sand material, new vegetation, and absorbent booms, which prevent material from being transported to the estuary. Direct exposure to trespassers and ecological receptors similar to the Unnamed Creek corridor also exists.
The Unnamed Pond exhibits similar hydrogeologic characteristics and risk pathways as the illustration of the conceptual model of the Wire Mill Pond area (thus, a separate figure was not prepared). Based on a 1907 topographic survey, the Unnamed Pond was historically riparian to the St. Louis River estuary at the mouth of a ravine complex. The Unnamed Pond is not visible on historical aerial photographs from 1939 to 1961, but it is visible on the 1972 historical aerial photograph.
2.3 Estuary Conceptual Site Models Two estuary CSMs were developed for the Remedial Investigation (RI) work plan to help guide investigation activities and provide a basis for understanding the effects of physical and environmental factors impacting the two delta areas in western Spirit Lake. The two delta areas are referred to as the Wire Mill Pond (WM) and Unnamed Creek (UC) deltas. A spit of constructed land extends eastward into Spirit Lake from the western shoreline between the UC and the WM deltas. The initial CSMs were updated during the preparation of the RI report (Barr, 2013a) and a third CSM diagram was developed to represent the Upper Wire Mill (UW) area, which is located between the UC and WM deltas and to the south of the spit. The CSM development process is iterative. These models have been updated as new data were obtained during investigation activities. The CSM discussions and diagrams presented in this report have been updated to include all data collected at the Site to date.
Separate CSM diagrams were prepared for three areas of the Spirit Lake estuary adjacent to the former steel mill site:
x The Wire Mill Pond (WM) Delta; the portion of Spirit Lake adjacent to the Wire Mill Pond discharge (Figure 2-5);
x The Upper Wire Mill (UW): the portion of Spirit Lake north of the Wire Mill Pond delta and adjacent to and south of the spit of land (referred to as the Upper Wire Mill) (Figure 2-6); and
x The Unnamed Creek (UC) Delta: The delta formed where the Unnamed Creek discharges to Spirit Lake, and the portion of the lake adjacent to the delta (Figure 2-7).
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2.3.1 Estuary Hydrology, Geomorphology, and Hydrodynamics The three CSM areas are located on the west side of Spirit Lake. The main channel of the St. Louis River through Spirit Lake is located along the far eastern shore, and is separated from an extensive shallow area in the middle of the lake by a barrier island along the inside turn of the thalweg. The open portion of Spirit Lake is separated from the western portion, where the deltas are located, by a secondary flow channel and Spirit Island along with a series of smaller barrier islands, shoals, and natural levees. These landforms are generally elongate and parallel to the secondary river channel through the middle of Spirit Lake, which includes a formerly dredged, abandoned shipping channel at the outlet of Spirit Lake.
The Estuary Site CSMs identify four geomorphic zones, which can be generalized into two sediment geomorphic zones based on water depth:
x Shallow Zone (includes the following three geomorphic zones) – 36 inches of water or less
o Land/Shore – above the normal water level (601.1 feet msl, USACE low water datum)
o Foreshore – 0 to 18 inches of water depth
o Nearshore – 18 to 36 inches of water depth
x Offshore Zone – greater than 36 inches of water depth
The defining characteristics for each of these four zones presented in the estuary CSMs were developed from the sediment sampling, bathymetric measurements, hydrodynamic modeling, biological sampling and a review of the sediment reworking/movement literature (Barr, 2014a). It should be noted that these geomorphic zone water depth ranges are not analogous to the biological activity zone target depths presented by the MPCA in its March 2014 project communication (MPCA, 2014b). The above information describes the current site conditions, not the post-remediation requirements presented in (MPCA, 2014b).
The hydrodynamics of the St. Louis River, and in particular the potential for sediment deposition or transport within Spirit Lake and the estuaries along the western shore have been studied extensively and modeled to develop a better understanding of current and future sediment transport mechanisms that may have an impact on potential Project alternatives. The hydrodynamic and sediment transport model for the site was developed using Delft3D. A detailed description of the model development and application is included in Appendix D. The following paragraphs summarize the primary findings from the development of the hydrodynamic model regarding the potential for sediment deposition or transport from river current, seiche, wind, and ice within the Estuary Site, as well as the effect of vegetation. Ice and river current are consistent throughout the Estuary Site, so those processes and effects are presented, for the entire river, in this Section. Seiche and wind processes and effects will be discussed in more detail in each individual CSM (Sections 2.3.3.1 through 2.3.3.3).
River flow has a significant role in the fluid velocities throughout the water column in each of the CSM areas of Spirit Lake. However, it has a limited role in sediment transport out of Spirit Lake and instead helps contribute to the overall sediment load in the estuary. One key recent weather event is important to the evaluation of the Spirit Lake dynamics and the evaluation of the remedial options. A significant
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volume of water flowed through Spirit Lake during the record-setting June 2012 flood, but net sediment removal was not observed within the study area. Instead, significant new (post-industrial) sediment deposition was documented within Spirit Lake as a result of this flood through the comparison of bathymetric surveys completed prior to and after the June 2012 flood event. Figure 2-8 shows the post-flood thickness of native (post-industrial) sediment. These observations and measurements were corroborated using the hydrodynamic and sediment transport model (Delft3D) described in Appendix D. Estuary modeling completed using data collected over the past four years identified that in general Spirit Lake is a net sink for fluvial sediment (sometimes also referred to as net depositional), although the amount of sediment deposited is dependent on the upstream load. The net deposition observed in Spirit Lake is consistent with historical observations when a majority of the lake was shallower and contained more aquatic vegetation. The current sediment load to the river is less than historical volumes, likely due to accumulation in the numerous upstream impoundments. However, during floods the sediment load can rise significantly, due to events such as upstream scour and dam failure. When these events occur, the Spirit Lake estuary is the first wide area of the river and a natural location for sediment deposition.
Lake Superior seiches affect the St. Louis River estuary from the harbor to the Site. Within Spirit Lake, the dredged shipping channel at the north end of the lake acts as a conduit for flow both into and out of Spirit Lake. Water level elevation changes caused by the seiche cycle results in significant volume of water exchanged between Spirit Lake and the St. Louis River, primarily through the dredged channel. Superposition of the seiche and the river discharge results in increased effective flow velocities during the falling limb of a seiche cycle, and decreased effective flow velocities during the rise of the seiche. Overall seiche activity increases the complexity of hydrodynamic conditions within the estuary, by affecting effective flow velocities and constantly changing water depths in the nearshore areas.
Wind-driven waves are a potential sediment transport mechanism for each delta and the spit. However, the shallow water depths, significant vegetation, and limited fetch within Spirit Lake limit the ability for significant waves to develop. Winds out of the north and the east present the largest potential for creating a significant wave event. Wave observations detailed in the Sediment Remedial Investigation Report (Barr, 2013a) were corroborated with modeled data discussed in Appendix D. Site observations and model corroboration indicate that wind-driven waves are not a significant sediment transport mechanism along the western shore of Spirit Lake, except on the foreshore where coarse sediment is reworked and fines are removed by wave action. Wave action within the foreshore areas of the Site will be considered during Project alternatives analysis because changing the shoreline and estuary conditions may change the impact of waves (i.e. changing sediment type, removing/adding vegetation, and/or increasing depth within the deltas).
The nearshore areas within the WM and UC delta areas are shallow water littoral zones with changing water depth due to the seiche activity and significant vegetation. Ice cover in this area frequently freezes to the bed and becomes anchored in place. Small localized ridges of sediment on the southern shoreline of the spit, and an ice ridge just off-shore of the eastern tip of the spit, indicate some ice movement that potentially was caused by wind, waves, seiche, and/or river flow. To evaluate the potential role of ice formation on sediment transport in these areas, ice formation and melt-out conditions were observed along the shorelines of the Site at various times in the winters of 2011 through 2014. The results of the ice
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observation field work are reported in the Barr RI report (2013a) and updated with information in Appendix E. Conditions during the four monitoring years represent a wide range of known climatic variability in the region, including the coldest winter (in terms of average temperature) in 139 years. During the four-year monitoring period no documentation of extreme ice conditions or extensive shoreline sediment removal within the Site was observed. Based on these observations, ice poses a negligible concern with respect to sediment transport along the Site shorelines.
2.3.2 Estuary Hydrogeology Shallow groundwater discharges to surface water in the Former Operations area (OUs and SAs) portions of the site (See Section 2.2.3.1 and 2.2.3.2). In addition, evidence of an upward groundwater flux has been described in some shoreline and nearshore areas of the Site, including a Shrub-Carr wetland complex, which is representative of a groundwater source and therefore an upward flux, on the northern shoreline of the UC delta (OU-M) area. Groundwater seeps have been observed along the shoreline – west of the railroad tracks in the Wire Mill Pond area, west of the tracks in the northern Unnamed Creek area and near the railroad tracks in the western OU-M Delta area – in these portions of the site at the base of the steep hillside beside the estuary shoreline these seeps act as a hydraulic head relief mechanism, resulting in limited driving head and likely a very small net flux.
However, the flux to or from the offshore portions of the estuary has not been previously studied. To resolve this data-gap, flux meters were installed in the off-shore regions of the estuary to measure the potential for off-shore groundwater-surface water exchange. The results of the flux meter study, which are included in Appendix F, showed a small, measurable, net downward flux from the lake into the sediment. While the velocity of the flow was very low, the downward flux was consistent in the offshore flux meter locations more than 200 feet from shore. These results suggest that the shallow groundwater at the site does not have any effect on pore water movement in the offshore portions of the site. Any potential regional influences associated with deeper groundwater were not observed in the estuary study, likely due to the extensive clay that is present below the Site. The measured flux is very small and net downward based on piezometer and flux meter measurements meaning that diffusion is the primary porewater flux mechanism, not advection. The primary conclusion from these analyses is that flux in the offshore areas is very small and therefore diffusion is the primary porewater flux mechanism, not advection in this area.
Ebullition is not a likely pathway of concern, based on observations that no ebullition was identified in any of the flux meters. Ebullition involves gas bubble transport of sediment upward through overlying sediment to the top of the surface water, where the bubble bursts and the sediment falls on top of the existing sediment surface.
Pore water samples collected from sediment within Spirit Lake were analyzed for the presence of PAH, metals, TOC, and black organic carbon sediment concentrations. The results of these analyses indicated that PAHs were more sorbed to Site sediments than would have been predicted by published equilibrium partitioning coefficients for organic carbon (EA, 2013), but metals pore water results were inconclusive.
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2.3.3 Description of Estuary Site Models 2.3.3.1 Wire Mill Pond (WM) Delta Conceptual Site Model The WM delta is located where the Wire Mill Pond discharges into the southwestern portion of Spirit Lake. As described in Section 2.3, the UM and WM delta areas are generally defined by the man-made spit of land on the north, a natural land barrier, wetland, and the main river channel on the south, and the shallow flats of eastern Spirit Lake on the east. The WM delta CSM is focused on the southern portion of the defined area and the UW CSM was developed for the northern portion of this part of Spirit Lake.
The Wire Mill Pond, which is upstream of the WM delta, was remediated in the 1990s to reduce the flux of contaminants and sediment from the pond to the river. Currently, the pond discharges to Spirit Lake through a narrow, sorbent-boom-lined outlet. As a result of controlling the source, the majority of the WM delta has post-industrial sediment at the surface. Non-native sediment was only identified at the surface of the WM delta in a small area along the shoreline where nearshore wave action and other factors inhibit the deposition of new sediment. The stratigraphy of the WM delta consists predominantly of silt near the surface, with layers of fibrous peat and clay near the shoreline. Silt, fibrous peat and clay are underlain by sandy silt grading into silty sand to a depth of at least 50 feet. Non-native (industrial fill) sediment occurs in thin layers (less than four feet thick, Figure 2-9) and was observed to be present only in the silt, clay and peat overlying the silty sand. COI migration is not anticipated to be a pathway of concern in the WM delta, either downward to the underlying sand or upward to the sediment or surface water through ebullition or advective flow. Post-industrial sediment covers the majority of the non-native sediment in the WM delta area of the Site. This material has gradually accumulated over time after being delivered from flow in the adjacent St. Louis River channel and by seiche flow. Little-to-no post-industrial cover has been deposited in an area extending eastward from the Wire Mill Pond outlet. This area likely receives little sediment because it is farthest from the main channel of the river where new sediment is being deposited and any material that settles in the nearshore is likely reworked by seiche flow and wave action.
Spirit Lake geometry and shallow water depths combine to limit the effect of wind-driven waves on the WM delta. Westerly and southerly winds are limited by a short fetch, while the spit provides protection from northerly winds. Shallow water depths and islands, including Spirit Island; limit the growth of waves from easterly winds. Wave height is further attenuated by bottom roughness due to vegetation and other subsurface features, including a significant amount of submerged logs and trees, located within the WM delta area.
Overall, the WM delta portion of Spirit Lake appears to be stable with respect to sediment impacts from COI due to upgradient source control, post-industrial sedimentation providing cover material, and protection from wind-generated waves by the land forms on the north, south and west.
2.3.3.2 Upper Wire Mill (UW) Conceptual Site Model The UW area is located south of the constructed spit of land that separates the UC delta from the UW and WM delta areas, and north of the WM delta area. The UW area is generally bounded by the spit of land on the north, the shallow flats of eastern Spirit Lake on the east, and the WM delta area on the south. The
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UW is a shallow-water area with a flat bottom and a significant number of submerged stumps, logs, and trees. The vegetation is considered to be a remnant from an area of emergent vegetation that has been seen in historical aerial photographs of the UW area. The UW area also includes two locations where historical dredging occurred. The first is the dredged channel located along the eastern side of the UC delta. This channel extends south past the spit, to the northeast portion of the UW area. The other dredged area is an irregular-shaped hole in the northwest portion of UW the area where the spit of land converges with the natural shoreline. It is generally understood that this hole was dredged to provide a water intake source for the former steel mill.
The UW area is located immediately downstream from the WM delta area. However, no evidence exists that would denote the presence of a historic or current source of potential non-native fill or other contaminants directly into the UW area. As noted previously, the Wire Mill Pond was remediated in the 1990s to reduce the flux of constituents and sediment from the pond to the river.
The stratigraphy of the UW area consists predominantly of silt near the surface, with an area of fibrous peat adjacent to the southeastern end of the spit. Silt, organic silt, and fibrous peat are underlain by silty sand and silt to a depth of at least 50 feet. Non-native sediment was observed to be present only in the silt and organic silt near the surface. The lateral and vertical extent of non-native sediments in the UW area has been defined, with irregular, isolated areas of surface sediment impacts including a thin buried layer in the dredged (water intake) basin and along portions of the western shoreline (Figure 2-9). COI migration, whether downward to the underlying sand or upward to the sediment or surface water through ebullition or advective flow, is not anticipated to be a pathway of concern. Post-industrial sediment, delivered from the adjacent St. Louis River channel by seiche and river flow, covers the majority of the non-native sediment in the UW area (Figure 2-8).
As was the case with the WM delta, the combination of Spirit Lake geometry and shallow water depths works to limit the effect of wind-driven waves on the UW area. Westerly and southerly winds are strongly fetch-limited, while the spit provides protection from northerly winds. Shallow water depths and islands, including Spirit Island; limit the growth of waves from easterly winds. In addition wave height is further attenuated by the abundant submerged stumps, logs and trees located within the UW area. Advective flow, ebullition and pore water dissipation appear unlikely to act as pathways of concern in the offshore portions of the estuary (generally more than 200 feet from shore), as discussed in Section 2.3.2.
The UW portion of Spirit Lake is stable with respect to sediment impacts from COI due to the lack of a direct source of non-native sediment or groundwater, post-industrial sedimentation providing cover material, and protection from wind-generated waves by the land forms on the north, south and west. The UW area is depositional under many river conditions, such as large flow and sediment load. The amount of sediment deposition is directly related to the river flow and upstream sediment load.
2.3.3.3 Unnamed Creek (UC) Delta Conceptual Site Model The UC delta consists of a broad, flat delta where Unnamed Creek discharges to Spirit Lake. The UC delta area is generally defined by the natural shoreline to the north and west, the constructed spit on the south, and barrier islands on the east near the dredged river channel.
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Surface sediment throughout a majority of the UC delta area, as well as Former Operations Area Site sediments, is impacted by PAHs. Work to address non-native sediment sources from the Former Operations Area portion of the Site, which will aid in the restoration of the UC delta, will be included within the Project alternatives that are the focus of this feasibility study. Non-native sediment deposition from up gradient areas of the Site in the UC delta area is expected to be eliminated when ongoing upland source controls are implemented.
The UC delta stratigraphy consists predominantly of PAH-impacted non-native sediments at the surface, including an area with cemented non-native sediments, underlain by thin layers of silty sand and sandy silt. The silty sand/sandy silt is underlain by fibrous peat on the western half to an unknown depth, and clay and silty sand on the eastern half of the UC delta to a depth of at least 50 feet. The non-native sediments are more than 10 feet thick near the shoreline with a thinning wedge extending eastward into the lake (Figure 2-9). The area of non-native sediments in the UC delta appears to be one fairly contiguous area, where little post-industrial cover has occurred (Figure 2-8). The non-native sediments occur in an area extending eastward from the Unnamed Creek outlet and surrounding shoreline to the dredged channel.
Wind-generated waves, predominantly from the north and east, are observed in the UC delta. These waves attenuate as they propagate onto the UC delta due to the increasingly shallow water. The primary effect of wind-generated waves within the UC delta area of the site occurs in the foreshore, where coarse sediment is reworked and fines are removed by wave action with little to no sediment transport observed. This observation was corroborated by model results.
Flow in the main river channel has little influence on sediment transport within the UC delta, due to the presence of the spit and the dredged channel. Observed and modeled flows from the 2012 flood show the primary river flowing past the UC delta, as the flow transited through the dredged channel.
Due to the proximity of the dredged channel to the UC delta, seiche flow can cause changes in water surface elevation and increased water flows into and out of the UC delta area. However, these flows are not expected to contribute to sediment transport to the river because velocities in the delta area are very low compared to the velocity in the dredged channel.
Advective flow, ebullition and pore water dissipation appear unlikely to act as pathways of concern, as discussed in Section 2.3.2
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3.0 Project Goals 3.1 Vision for Success The vision for a successful Project at the Site is defined in the Great Lakes Legacy Act funding request as one that:
x Meets the site specific Remedial Action Objectives (RAOs) as further defined in this Section;
x Contributes to minimizing or eliminating beneficial use impairments, as defined by the St. Louis River System Remedial Action Plan (SRL-CAC, 1992; LimnoTech, 2013) within the Estuary Site;
x Supports betterment through improvement of aquatic habitats in a manner that would not normally be included in the RP Superfund Process while incorporating concepts from the St. Louis River Habitat Plan (SLR-CAC, 2002) and the Spirit Lake Conceptual Habitat Restoration Plan (LimnoTech, 2012); and
x Positions the former U. S. Steel Duluth Works property (Former Operations Area of the Site) for brownfield redevelopment while minimizing the extent of areas used to consolidate and manage historical impacts.
As noted in Section 1, the goal of this FS has been to develop and consider a variety of alternatives that achieve this vision, with varying degrees of effectiveness and a range of costs, while taking advantage of potential synergies associated with a combined Former Operations Area and Estuary sediment Project. The FS process allows stakeholders and all the parties involved to develop a Project that can be designed and implemented to achieve an acceptable outcome that is consistent with this vision.
3.2 Overview of Remedial Action Objectives (RAOs) To achieve the vision of success for this Project, the work will be focused on achieving a carefully prescribed set of Remedial Action Objectives (RAOs). These RAOs are the numerical and qualitative criteria that, when completed, would provide protection of human health and the environment. The RAOs for this Project include (MPCA, 2014b):
Ecological Receptors
x Reduce risks to benthic invertebrates by reducing sediment concentrations of COIs to protective levels.
x Reduce risks to other aquatic organisms (plants, fish, amphibians, reptiles, birds and mammals) from direct exposure to COIs by reducing concentrations of COIs in sediment and surface water to protective levels,
x Reduce risks to fish, birds and mammals due to bioaccumulation of COIs.
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Human Health
x Reduce human health risks associated with exposure to COIs through direct contact with sediments, inhalation, and incidental sediment ingestion by reducing sediment concentrations of COIs to protective levels.
x Reduce human health risks associated with exposure to COIs through direct contact with soil, inhalation, incidental ingestion, and food chain in OU-S, OU-Q and tar areas T10 and T11 in OU-A.
Surface Water
x Achieve surface water standards for the project COIs for waters leaving the Site, within the Site, and for project-defined locations adjoining work areas in the estuary, that contribute to the overall water quality of the St. Louis River. Details will be developed in the design phase and during permitting.
x Reduce risk to surface water in OU-S and OU-Q by preventing transport from run off.
3.3 Former Operations Area Site Remedial Action Considerations To achieve the vision of success for this Project the work at the Former Operations Area Site will be geared toward achieving the following RAOs, as well as the following additional considerations:
x Providing a stable water course for stormwater conveyance and discharge that achieves the objective of allowing surface waters to meet applicable water quality standards. The final surface water configuration in the Site area will depend on the selected alternative, and the specifics will be determined during the design phase.
x Preserve upland areas for future economic redevelopment.
x Improve habitat (betterment).
Each of the Former Operations Area RAOs and considerations are described in further detail below.
3.3.1 Protect Human Health and the Environment Protection of human health and the environment guides the FS evaluation process and is a fundamental component of the Project RAOs listed in Section 3.2. Development of alternatives and the analysis of those alternatives must take into consideration the potential exposure pathways for humans and ecological receptors to potential chemicals of concern in the environment and the risk associated with these potential exposures.
In accordance with the FS work plan (Barr, 2012) and Agency guidance, ecological risk screening and human health risk screening evaluations have been performed to identify the nature, extent, and magnitude of potential impacts to human health and the environment based on MPCA-provided criteria. As described in the RAOs (Section 3.1) environmental remediation approaches that are identified by this FS must be protective of human and ecological receptor pathways specific to the Site and its setting.
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U. S. Steel updated both the Human Health Risk Evaluation and Ecological Baseline Assessment (HHRE and EBA) for impacted sediment and soil encompassed by the Former Operations Area portion of the Site within the October 2013 RIA (URS, 2013). Risk assessment findings relevant to this FS are discussed in the following sections.
3.3.1.1 Human Health Risk Evaluation Potentially complete human health exposure pathways in the Former Operations Area SAs were primarily associated with terrestrial areas with potential direct exposure to impacted soil. Exposure to surface water and sediment within the aquatic portions of the SAs is limited for human receptors as the aquatic portions of the Former Operations Area SAs present narrow accessibility or recreational opportunities to swim, drink, fish, or otherwise be exposed. Similarly, exposure to groundwater was not considered a complete exposure pathway as there are no current or projected uses of groundwater at the Site.
Potentially complete exposure pathways identified in the Former Operations Area HHRE included:
x Incidental ingestion, inhalation and dermal exposure to impacted near-surface soil (less than two feet below grade) by future industrial workers, future construction/utility workers and trespassers;
x Incidental ingestion, inhalation and dermal exposure to impacted subsurface soil (greater than two feet below grade) by future construction/utility workers; and
x Inhalation of indoor vapors by future industrial workers from impacted soils.
The Former Operations Area HHRE identified potential cancer risks for one or more receptors exceeding the MPCA target risk level of 1 x 10-5 in all SAs except OU-Q, which was determined to pose an ecological risk. Potential cancer risks exceeded the USEPA upper risk level of 1 x 10-4 at the CDA, T-10, and Tar Between I&J. Hazard indices were less than 1.0 in all SAs. PAHs were the primary contributors to the risk values in all areas where risk exceeded 1 x 10-5.
The MPCA subsequently provided comments to the HHRE component of the October 2013 RIA in a memorandum dated February 2014, (MPCA, 2014a). The MPCA generally accepted the Former Operations Area HHRE findings in their comments and stated that revision of the evaluation was unnecessary if proposed remedial actions would address items where exceptions were noted related to trespasser risk in the CDA and trespasser/potential recreational user risk in OU-Q.
The HHRE-based RAOs for the Former Operations Area SAs will focus on reducing human health risks associated with exposure to COIs through direct contact with soil.
Industrial Soil Reference Values (ISRVs) will serve as the primary PRGs for soil to allow for future industrial redevelopment for OU’s and SA’s in the Former Operations areas of the Site. Secondary Recreational Soil Reference Values (RSRVs) may be applied as PRGs in certain terrestrial areas of the SAs if recreational access is provided as an outcome of response actions.
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x
x The SRVs selected to meet the Human Health RAOs with respect to direct human exposure to upland soil at each of the Study Areas under the anticipated future property use are summarized in Table 3-1.
Direct contact with impacted sediments was considered an incomplete pathway in the HHRE. Further, exposure through the human food chain via uptake from impacted sediment was not believed to be a significant pathway for the Former Operations areas of the Site as fishing and hunting are not associated with the SAs. As such, specific PRGs for human health risks associated with direct contact to impacted sediments have not been established. Human health exposure risk from impacted sediment in the SAs will be addressed through implementation of measures to mitigate ecological risks.
3.3.1.2 Ecological Baseline Assessment An updated ecological risk evaluation was also presented in the 2013 Upland RIA (URS, 2013) that identified potential risks to relevant ecological receptors in specific areas of the Site. A summary of potential ecological risks is presented in Table 3-2. Attainment of aquatic-based RAOs will address ecological risks in both the Former Operations Area Aquatic and Scrub-Shrub Forested Wetland environments identified in Table 3-2. Since the sediment numerical PRG criteria for the protection of potential ecological receptors within the aquatic areas of the Former Operations Area of the Site match those of the Estuary Site, further discussion pertaining to the development of sediment PRGs is contained in Section 3.4.1.2.
Assessment endpoints for the Terrestrial Habitat were terrestrial birds and mammals that may forage in this area and be exposed to site-related chemicals through ingestion of impacted prey and soil. In all instances the highest hazard quotients (HQs) were observed for invertivorous birds and associated with metals and PAHs. Risks to plants were identified as low in the Terrestrial Habitat. The updated ecological risk evaluation also found a high level of uncertainty in evaluating risks associated with exposures to soils in the Terrestrial Area due to poor habitat quality and high organic carbon in soils which limit PAH bioavailability. Thus, it was concluded that there is a potential for ecological risks in the Terrestrial Habitat.
Reducing risks to birds and mammals due to bioaccumulation of COIs is the only ecological RAO that applies to the Terrestrial Habitat. A remedy that utilizes tiered SRVs as PRGs (for both industrial and recreational end-use scenarios) for reduction of human health risk will also reduce ecological risk within the Terrestrial Habitat. In addition, reducing soil concentrations and/or interrupting exposure pathways will reduce ecological risk.
3.3.1.3 Extent and Magnitude of Former Operations Area Impacted Media Using the Soil SRVs and the Sediment PRGs defined above, elevated PAHs and metals were used as the primary indicator for defining the extent of impacts at the five Former Operations Area OUs and four SAs as shown on Figure 3-1. Data collected as part of the Remedial Investigation, past investigations, and the conceptual model for the nature of deposition were used to identify the lateral extent and the thickness (vertical extent) of both soil and sediments in the Study Areas. In general terms, the lateral extent of sediment impacts is clearly defined by Site topographic constraints on the areas of historical deposition, while the lateral and vertical extents of the soil impacts were defined by the interpolation of data points
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from prior investigative work. Collectively, these areas comprise the limits of impacted material to manage in order to protect human health and the environment. The extents of specific Study Areas are summarized in Table 3-3.
3.3.1.4 Extent of COIs related to PRGs The areal extent of soil and sediment requiring a response action is determined by COI concentrations that exceed PRGs (MPCA, 2104 a,b). PRGs have been established for PAHs, lead, copper, and zinc, and represent a subset of the COIs. Analytical testing has been conducted for a longer list of parameters as presented in Table 1 of the RI Report (Barr, 2013a) and Section 2.5 of the Upland RI Report (URS, 2013). The analytical results have been compared to SRVs, SQTs, and SSVs to determine a list of COIs (Barr, 2013a; URS, 2013).
Concentrations of COIs from sediment samples were compared to concentrations detected in sediment samples collected from throughout the estuary during other investigation conducted by the MPCA. The data comparison identified potential sediment COIs, while identifying other constituents that are not associated specifically with potential Spirit Lake sediment Site management and FS evaluation needs. These screened out COIs include: PCBs, dioxin/furans, cadmium, and mercury. A focused list of sediment COIs was included in Table 14 of the RI Report (Barr, 2103a).
The list of COIs from the OUs and SAs for this FS evaluation are listed in Section 1.2.4 and are presented by area on Table 3-4. The extent of the COIs for these areas are shown on Figure 3-1. The COIs consist of PAHs and various metals. The areas where metals and PAHs exceed screening criteria are largely co-located. Therefore, a remediation of the parameters for which PRGs have been established will result in remediation of all COIs.
3.3.2 Prevent Migration and Transport of COIs and Maintain Surface Water Quality
If sediments with COIs remain in or near stormwater drainageways, the RAO of preventing migration and transport of COIs while maintaining compliance with surface water quality will be obtained in part by providing a stable water course for storm water passing through the Former Operations Area of the Site. FS alternatives will be evaluated with respect to the manner in which a stable water course will also help to ensure the long-term viability of the Estuary Site RAOs and provide protection of potential estuary habitat enhancements. Eliminating the potential for residual materials that may remain at the Former Operations Area of the Site from migrating to the Estuary Site via stormwater is an important component in the overall success of the Project and a key reason for linking the proposed work at the two areas of the Site (Operations area and Estuary). Providing a stable water course may require physical separation of the stormwater from residual materials in the Operations Area of the Site containing concentrations of COIs in excess of the sediment management goals. In addition to physical separation, the channel must be designed to pass a large storm event, referred to as the design storm. Proposed site grades and channel improvements associated with the final remedy will be designed to effectively convey large storm events.
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A naturally stable water course designed to convey run-off from this watershed would need to achieve several objectives, including:
x Flood management to limit adverse on-site impacts from flooding and to avoid raising flood levels downstream of the site;
x Management of smaller, more frequent storms as well as the Unnamed Creek base flow to avoid localized erosion or other damage and minimize routine maintenance; and
x Integration of the function of potential remedies, such as caps and CDFs within the storm water conveyance system so that all components function effectively and remain protective.
Criteria used for defining and designing the storm water conveyance components of the Project are summarized in Table 3-5.
3.3.3 Preserve Areas for Economic Development The goal of facilitating potential future uses of the Site, including the potential for industrial redevelopment on portions of the U. S. Steel Former Operations Site area, will also be considered when evaluating potential Project Alternatives. The future redevelopment area would be offset from the shoreline area, so that redevelopment could be compatible with habitat restoration activities in the estuary.
3.3.4 Improve Habitat (Betterment) Another important reason for considering the Former Operations Area and Estuary sites as a combined Project for the purpose of this FS was to allow for potential synergies between betterment in the portions of the site that are currently Former Operations Areas, but have the potential to be returned to open water and the existing Estuary. This was a key opportunity identified in the St. Louis River conceptual plan (LimnoTech, 2012). While this is included as a Former Process Area goal, the potential for habitat improvement originates in the Estuary. Thus, this goal is described in further detail along with the Estuary goals in Section 3.4.3.
3.4 Estuary Remedial Action Considerations Similar to the Former Operations Area of the Site, the Estuary Site will have specific remedial action considerations in addition to the overall RAOs. The RAOs and considerations will need to be met for the Project to achieve the overall vision for success. The Estuary-specific considerations will include:
x Reduce beneficial use impairments for St. Louis River Area of Concern
x Improve habitat (betterment)
The Estuary RAOs and considerations are described in further detail in the following paragraphs.
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3.4.1 Protection of Human Health and the Environment The RAO for protection of human health and the environment includes the development of Project-specific, numeric criteria that will adequately protect future human and ecological users of the estuary resources while also improving the overall use of the area. These two topics are discussed separately in the following sections.
3.4.1.1 Human Health Risk Evaluation Potentially complete exposure pathways for human exposure were presented in the Human Health Risk Evaluation (HHRE) in the RI (Barr, 2013a). These pathways included:
x Incidental ingestion or inhalation of sediment containing COIs while wading or swimming;
x Dermal exposure to sediments; and
x Fish consumption.
The HHRE concluded that adverse human health effects from exposure to sediment by incidental ingestion and dermal contact were not expected based on reasonable exposure assumptions. Potential risks are already partially controlled via institutional controls, including fish consumption advisories in the area, and additional institutional controls will be evaluated during the alternative evaluation process.
Since the completion of the RI, additional assessment of potential human health risks have been explored through the calculation of Benzo(a)pyrene [B(a)P] equivalents for a combination of exposure scenarios, and comparison of the B(a)P equivalent values to site data. As noted in the updated human health risk screening evaluation (Barr, 2014b), the Estuary Site sediments with B(a)P equivalents values exceeding B(a)P equivalents predicted to be protective of human health lie within the aerial extent of Estuary Site sediments that have the potential to impact ecological resources (as described in Section 3.4.1.2). Therefore, a remedy that reduces sediment concentrations of PAHs for ecological receptors will also reduce human health risk. Thus, the ecological risk-based limits for improvement of the Estuary Site provide the basis for the development and consideration of alternatives that could achieve the vision of success for this Project.
3.4.1.2 Ecological Risk Screening Potential ecological exposure pathways of interest include benthic invertebrates contacting and consuming sediment and surface water; wildlife contacting or consuming sediment; wildlife consuming aquatic plants, fish, or invertebrates; and aquatic plants contacting sediment and fish. As stated in the RI (Barr, 2013a), the primary focus of sediment management activities at the Estuary Site will be to reduce the potential for unacceptable risk to these ecological receptors. This area of focus has been incorporated into the RAOs for the Project as listed in Section 3.2.
To establish numerical criteria for the RAO for the protection of potential ecological receptors within the Estuary Site, preliminary remediation goals (PRGs) were provided by MPCA (MPCA, 2014b). Project alternatives will be targeted at sediments containing COIs at concentrations exceeding the PRGs.
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The PRGs were set at the midpoint between the Level I and Level II MPCA Sediment Quality Targets (SQTs) (MPCA, 2007). Level I SQTs identify concentrations for COIs below which adverse effects to benthic organisms are unlikely. Level II SQTs identify concentrations for COIs above which potentially adverse effects to benthic organisms are likely to occur (MPCA, 2007). The midpoint between these two values was chosen for PRGs to be protective of benthic receptors when applied on a point-by-point basis. The PRGs for sediment (MPCA, 2014b) are summarized in Table 3-6.
These PRGs were developed to be used within the potentially bioactive zone, which varies in thickness based on habitat type. The potentially bioactive zone is defined by the MPCA to have a specified thickness of uncontaminated ecological substrate for the viability of vegetation, benthic organisms, and burrowing wildlife (MPCA, 2014b). Depending upon the habitat type and receptors expected to be present, different substrate thicknesses were determined to be applicable as shown in Table 3-7.
3.4.1.3 Extent and Magnitude of Estuary Impacted Sediment The lateral and vertical extent of sediment exceeding PRGs for the COIs has been defined based on a point-by-point comparison of all samples collected in the Estuary Site (Figure 3-1). The extent of sediment exceeding the ecological risk-based PRGs includes all sediment exceeding the human health risk-based values, as described in Section 3.4.1.1, and therefore also defines the area of Estuary Site sediments to be managed in order to protect human health and the environment for consideration of Project Alternatives in this FS.
3.4.2 Reduction of Beneficial Use Impairments for the St. Louis River Area of Concern
Because the Site is located within the St. Louis River Area of Concern (AOC), remediation work, once completed, is anticipated to positively aid efforts by resource management agencies to address beneficial use impairments (BUIs) in the larger AOC. Identifying Project Alternatives that meet the RAOs and also have the potential to reduce BUIs within the St. Louis River AOC is an important goal for this Project. The current BUIs include the following (LimnoTech, 2013):
x Restrictions on fish and wildlife consumption
x Excessive loading of sediment and nutrients
x Degradation of fish and wildlife populations
x Beach closings
x Fish tumors or other deformities
x Degradation of aesthetics (this BUI was removed August 29, 2014)
x Degradation of benthos
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x Restriction on dredging activities
x Loss of fish and wildlife habitat
These BUIs are related to the presence of COIs from various sources along the river, as well as physical loss and degradation of habitat in some portions of the AOC. The AOC will be delisted when these beneficial uses have been restored, as indicated through achievement of established delisting targets (LimnoTech, 2013).
COIs in sediment at the Site contribute to beach closings, degradation of aesthetics, degradation of benthos, loss of fish and wildlife habitat, and to restrictions on fish and wildlife consumption. Sediment management and remediation at the Site will be designed to address local contributions to these BUIs, as outlined in Section 3.4.1.2 for protection of ecological resources, and will therefore support removal of BUIs and ultimate delisting of the larger Area of Concern. It should be noted that the work at the Site can only address these issues within the Site and immediate local area, while the AOC covers a much larger area that encompasses impacts and BUI issues not related to, or within the scope of the subject Site remediation plans.
3.4.3 Improve Habitat (betterment) The Habitat Characterization Report (Barr, 2013b) found that the Site contains a variety of aquatic, shoreline, and terrestrial habitats with varied quality. The Unnamed Creek shoreline was observed to have better habitat quality, with dense vegetation and a high level of species diversity. Lower quality habitat was observed along the shoreline of the Wire Mill Pond, with low diversity of vegetation. Non-native, invasive species were observed onshore in both areas.
Habitat betterment components consistent with the Spirit Lake Conceptual Habitat Restoration Plan (LimnoTech, 2012) could be incorporated in the selected alternative to provide a shoreline that is similar to native estuary shorelines and a productive substrate for local flora and fauna. The habitat betterment components for the selected alternative will be discussed in more detail in the proposed Project plan. The subsequent Project design will likely include both the habitat enhancement components and habitat mitigations, if necessary, as determined during Project permitting.
Potential betterment components that could be incorporated into the Project are included in the alternative screening and detailed analysis evaluation processes (Sections 4 and 5).
3.5 Other Project Considerations In addition to the primary objectives of protecting human health and the environment, reducing beneficial use impairments, improving the habitat of Spirit Lake, and providing for future economic development; the Project will consider several other factors including:
x Consideration of cultural and recreational values for the region;
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x Providing an example for future sediment projects by considering green and sustainable principles;
x Consistency with U.S. EPA’s Principles for Managing Contaminated Sediment Risks at Hazardous Waste Sites, OSWER Directive 9285.6-08 (EPA, 2002);
x Complying with environmental review and oversight requirements; and
x Maintaining a Project Schedule that will facilitate completion of the Project in the GLLA program.
Each of these items is described below.
3.5.1 Consideration of Cultural and Recreational Values The cultural significance of Spirit Lake is an important factor to consider in developing the vision for the overall success of this Project. The Site is adjacent to Spirit Island, owned by the Fond du Lac Band of Lake Superior Chippewa, which is an important part of the history of the Ojibwe people and considered a sacred place (LimnoTech, 2012). Spirit Island and the lands owned by the Fond du Lac Band of Lake Superior Chippewa are beyond the Project Area and are not anticipated to be directly affected by a potential Project remedy.
The Estuary also hosts a variety of potential recreational activities, including boating, fishing, and bird watching. To provide the opportunity for continued recreational activities in the Estuary, the selected alternative should be compatible with these and other outdoor activities. The constructed Project at the Estuary site could have the potential to increase public access to natural areas of the Site, and this factor will be evaluated during design.
Two distinct bathymetric depression features at the Site are considered important for recreational fishing. The first is a bathymetric “hole,” which has greater water depths than the surrounding nearshore areas, located near Wire Mill Delta. This depression was created by dredging for a water intake and currently is used recreationally for fishing. The second bathymetric feature is a remnant channel on the north side of the Project footprint. This channel has remained largely unchanged likely due to seiche events from the north minimizing sedimentation and filling of this feature over time. Both of these features should be maintained to the extent practical when considering the Project alternatives.
3.5.2 Consideration of Green and Sustainable Principles Conservation of natural resources, waste minimization, and reduced energy consumption are all important factors to be considered in the selection of the Remedial Alternative for the Project. When applied to environmental improvement projects, conservation and impact minimization concepts are often referred to as “green remediation.” EPA guidance identifies many concepts for making remediation greener (EPA, 2010). Examples include:
x Conservation of natural resources;
x Reusing materials otherwise considered waste;
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x Maximizing energy efficiency;
x Decreasing air emissions;
x Conserving water resources;
x Planning work to include consideration of green practices materials; and
x Helping to increase the understanding and awareness of green technologies.
As stated above, goals for this Project include habitat enhancement. While the Project will involve some disturbance of natural resources at the Site during construction, it will produce overall benefits for fish and wildlife, and will improve plant communities, in the estuary. It is anticipated that the Project will create additional habitat and recreational opportunities that do not currently exist. Measures may also be taken to minimize the amount of waste requiring disposal, and thus reduce the amount of energy used and air emissions produced in transporting. Waste minimization should be balanced with requirements to ensure that the Project objectives are achieved. Opportunities to optimize water conservation during the Project will also be assessed.
Specific opportunities for green remediation will be incorporated into the Project alternatives as appropriate. These may include methods for increasing energy efficiency, decreasing air emissions, planning with green concepts in mind, and increasing public awareness. These and other green remediation components can produce environmental benefits when their use is balanced with remedy protectiveness, implementability, and cost. Careful consideration must be given to where and how green components can be incorporated, while maintaining compatibility with the Project objectives, with regulations, and with Project schedule and budget.
3.5.3 Consistency with EPA Sediment Management Principles The U.S. EPA has published principles (EPA, 2002) for site managers to make scientifically sound and nationally consistent risk management decisions for impacted sediment sites. This OSWER Directive presents eleven risk management principles that were used to develop and evaluate the Estuary sediment remedies discussed in Sections 5 and 6.
3.5.4 Compliance with Oversight and Environmental Permitting Requirements Oversight and permitting of the Project could include Federal, State, and Local provisions. The potential permits that may be necessary to complete the work are presented in Appendix G.
Because the Former Operations Area Site work is being completed under the terms of a Consent Decree with the MPCA, the MPCA has the authority to waive or defer some of the administrative requirements of State permitting to facilitate the timely and efficient implementation of a selected alternative. However, substantive permit requirements will still be identified as ARARs (Appendix H). Local ordinances will still need to be followed including any potential construction permitting that may include operating restrictions to minimize noise, light, or other disruptions to the community.
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Given that the Project activities within Spirit Lake are expected to affect large areas of open water and wetlands, it is anticipated that compliance with the Clean Water Act and Minnesota regulations regarding water resources and wetlands will constitute the most substantive requirements for coordination and documentation and may entail mitigation. State regulations regarding dredged material placement and federal and state disposal regulations will also require significant coordination, as will permitting of process water discharges for dredging and dewatering. Forestry, sensitive species, and cultural resources permitting/coordination will also require documentation and coordination. Section 6.2 of this FS provides a detailed discussion of anticipated permitting requirements for the preferred Project alternative.
3.5.4.1 Environmental Review Although some permitting requirements may be waived, the environmental review process will still need to be considered for Project work at the Site. National Environmental Policy Act (NEPA) established a framework for environmental planning and decision-making by federal agencies. Federal agencies must conduct a complete environmental review prior to undertaking a major federal action, which will significantly affect environmental resources. Under NEPA, federal agencies are required to complete this environmental review by preparing either an environmental assessment or environmental impact statement, both of which assess the potential for, and significance of, environmental impacts from alternative courses of action. Federal approval of remediation activities to remove COIs from the Former Operations Area of the Site would require the preparation of either an environmental assessment or environmental impact statement depending on the significance of environmental impacts.
As part of MPCA’s environmental review process, the Project will require completion of an Environmental Assessment Worksheet (EAW). This review procedure uses a worksheet with a standardized list of questions to screen Projects that may have the potential for significant environmental effects. The EAW is subject to a 30-day public review period prior to the decision on whether the Project requires an Environmental Impact Statement (EIS).
3.5.5 GLLA Scheduling Considerations The final component of the vision for a successful Project is that the work must be completed in a timely manner. This will begin by completing this FS and all associated alternative evaluation components in a time-frame that will ensure the availability of GLLA funding for the Project implementation. The use of GLLA funding is expected to further accelerate the rate of on-site Project activities with the goal of completing all of the Project work within two construction seasons.
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4.0 Technology Screening 4.1 Technology Identification and Screening Process Potential technologies for addressing conditions at the Estuary and Former Operations Area Sites were identified through many sources, including guidance specifically developed for the remediation of contaminated soil and sediment sites (EPA, 2005; ITRC, 2014). Information collected during the RI site characterization and the development of the CSMs was used to identify feasible technologies for the Site.
The screening of potential technologies and process options for management of sediment and water impacts associated with the Site is described in Sections 4.2 and 4.3 respectively. A qualitative approach was used to screen technologies using a three-part ranking system where each technology was evaluated on protectiveness, effectiveness, implementability, and relative cost, using the following criteria:
x Effectiveness was evaluated by the predicted ability of the alternative under consideration to ensure long-term protection of human health and the environment, while minimizing short-term impacts during implementation. For this screening, effectiveness was measured by whether the technology could potentially meet the Former Operations Area RAOs or Estuary SMGs; the overarching goals for the Project as defined in Section 3. Effectiveness also considered whether a technology could incorporate habitat betterment or redevelopment of the Site.
x Implementability was evaluated by considering both the technical and administrative feasibility of a technology. Technical feasibility includes: the ability to achieve the remedial goals; the avoidance of creating additional risk during implementation (risk of remedy); the ability to handle the necessary quantities or reach required depths; the need for specialized equipment; the time needed to meet remedial goals; the degree of disruption in the Project area; and the ability to undertake an additional remedial action if the selected remedy fails. Administrative feasibility includes consideration of the permits needed for technology implementation; availability and capacity of treatment, storage, and disposal facilities; availability of required equipment or workers; and coordination with applicable agencies and stakeholders. For this screening, the implementability ranking of each technology focused on the degree of disruption in the Project area, the time needed for permitting and implementation, the estimated quantities of material handling or area required, and the need for specialized equipment or technical knowledge.
x Relative costs used for the technology screening were based on engineering judgment, rather than detailed estimates. The cost evaluation considered direct and indirect expenses such as costs for dredging and capping, transportation, treatment and/or disposal of sediment and long-term costs for operation, maintenance, and monitoring during and after the implementation of the technology.
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4.2 Sediment Technologies Technologies for addressing estuary sediment, and Former Operations Area sediment and soil, impacts were identified in USEPA guidance (EPA, 2005). The sediment technologies and other controls screened in this Section include:
x Institutional Controls
x Natural Recovery
x Capping
x Excavation and Removal
x Disposal
x In-Situ Treatment
The technology and process screening results are summarized in Table 4-1 for sediments, and soils, where appropriate. Technologies and process options deemed most favorable were retained for assembling the alternatives described in Section 5.
4.2.1 Institutional Controls Institutional controls in the form of an environmental restrictive covenant may be needed to prevent unacceptable exposure and contact with the impacted sediment and soil or to minimize future disturbances in areas where impacts are managed in place or residuals remain at depth. Other potential forms of institutional controls may include governmental regulations or permitting limitations.
4.2.1.1 Applicability to the Former Operations Area of the Site Former Operations Area institutional controls may include land use restrictions (e.g. restriction on types of development, excavation, etc.). Institutional controls are anticipated to be included as a component of most Former Operations Area Site alternatives; the specific restrictions will depend on the final Site alternative that is selected.
4.2.1.2 Applicability to the Estuary Site Institutional controls are also anticipated to be included as a component of the Estuary Site alternatives. The specific restrictions will depend on the selected Site alternative. Institutional controls may include waterway use restrictions (e.g., no wake zones, no anchor zones, etc.), land use restrictions (e.g. restriction on construction of boat landings or docks), permitting restrictions on future dredging or fish consumption advisories or fishing bans (EPA, 2005).
4.2.1.3 Screening Effectiveness: Institutional controls are effective for minimizing human exposure at the Site, and would be effective at achieving Estuary SMGs and Former Operations Area RAOs when used in combination with
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other remedies. Institutional controls may be used to protect the selected remedy from physical disturbance.
Implementability: Institutional controls are easily implemented in a short time frame and would not cause disruption to the site or surrounding community. However, institutional controls may limit the potential for future betterment activities in the estuary or future redevelopment of Former Operations areas.
Relative Cost: The cost to implement institutional controls alone is considered to be very low compared to other remedial approaches, with no construction costs. However, institutional controls will likely be integrated with other technologies.
4.2.1.4 Screening Results Institutional controls are retained for the assembly of alternatives based on the likelihood that they will be a required component for use with other technologies.
4.2.2 Natural Recovery Natural recovery (NR) is a technology that uses ongoing naturally occurring processes to contain, destroy or reduce the bioavailability of COIs by physical (burial and dispersion), chemical (sequestration and transformation), or biological mechanisms (biodegradation). NR can reduce COI concentrations to below levels of concern, but time frames can be longer.
Under the correct conditions, NR processes can be accelerated through enhanced natural recovery (ENR). In Former Operations Area sediments, ENR amendments may include a biological stimulant (i.e., a degradable carbon source) or an oxidation agent injected into the surface of the soil or sediments to enhance plant growth or other actions that would promote degradation. Accelerated remediation of deeper impacts to soil and sediment are addressed in the discussion of in situ treatment (Section 4.2.6).
In estuary sediments, ENR amendments may include a thin-layer sediment cover or injection of a carbon-based sorbent or incorporation of other materials into the sediment surface. ENR accelerates the process of physically isolating COIs that is already occurring naturally with sediment deposition. The ENR amendment speeds the development of a clean sediment layer at the surface, which results in the reduction in surface chemical concentrations and facilitates the re-establishment of benthic habitat (ITRC, 2014).
NR or ENR can be implemented as a sole technology or may be part of a larger remedy for a Site and may be combined with other technologies such as capping or removal. Institutional and/or engineering controls are commonly employed in conjunction with NR to minimize exposure during the recovery period and the potential for disruption of the natural recovery processes.
Natural recovery has the following advantages over other remedial approaches (EPA, 2005):
x It is easily implementable, and is less disruptive and expensive than sediment removal because it does not require material handling, dewatering and disposal.
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x ENR quickly reduces exposure to COIs and provides a clean substrate at the sediment surface for benthic recolonization.
x NR and ENR do not result in disturbance of sediments and short term release of COIs to the water column as may occur during sediment removal.
The main limitations of NR or ENR include the following:
x COIs are left in place, so restrictions to site use, monitoring, and replenishment of an ENR cover may be needed.
x The time frame for NR or ENR to meet SMGs may be longer than for sediment removal or capping.
x Sediment stability must be demonstrated where NR and ENR are selected as the remedial technology.
4.2.2.1 Applicability to the Former Operations Area of the Site NR is the technology selected in the ROD for Former Operation Area sediments, including sediment in the Unnamed Creek channel (OU-I, OU-L, and OU-M) and the wire mill dredge material (OU-Q) (MPCA, 1989). This initial decision was affirmed with the acceptance of a treatability study that showed limited potential for treatment of the non-native sediments in these operable units (Barr, 1990). Vegetation has returned to many of these areas over the years and some natural recovery is occurring. While the rate of recovery is slow, and could likely be enhanced with the addition of nutrients or other amendments, the potential for exposure to these areas is limited by the vegetation that has been established.
4.2.2.2 Applicability to the Estuary Site NR is also the technology described in the ROD for estuary sediments (MPCA, 1989). NR processes have been occurring at the Estuary Site; reducing COI bioavailability and mobility, primarily by the natural deposition of new sediment layers over impacted sediments (See Section 2). However, NR on its own may not meet the MPCA PRGs (MPCA, 2014b) at all locations. NR and ENR are most applicable to areas that have very thin sediment layers where concentrations exceed the PRGs, and/or are not significantly greater than the PRG concentration levels, where the sediment bed is stable, disturbance to the sediments is unlikely, and the rate of new deposition is adequate.
4.2.2.3 Screening Effectiveness: NR processes have been effective at achieving RAOs at a variety of petroleum-impacted sites and have been effective at achieving the estuary PRGs through sediment deposition over portions of the estuary as shown on Figure 2-8 and discussed in (Barr, 2013a). NR may be marginally effective in the Former Operations Area due to the thickness of the impacts and the limited potential for degradation in the subsurface. The PRGs could be achieved in the Estuary Site within a shorter time frame than NR by implementing ENR at additional locations. NR and ENR alone will not meet PRGs at all locations, but these technologies are considered highly effective when used in select areas of the estuary and when combined with other technologies and institutional controls.
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Implementability: NR is a naturally occurring process that is highly implementable, and is likely already occurring within some areas of the estuary. Implementing ENR is expected to only cause moderate disruption relative to sediment removal and conventional capping. ENR would be technically challenging in areas of deep Former Operations Area Site sediment accumulation and consolidated coke fines, but could be implemented with standard sediment remediation equipment and resuspension controls in the Estuary Site.
Relative Cost: NR can be implemented for relatively no cost other than routine monitoring. Costs for ENR are low relative to most technologies, although somewhat higher than NR because of the enhancements that are added to the system.
4.2.2.4 Screening Results NR and ENR are both retained for assembly of alternatives as components that may be effective in portions of the Estuary Site or in combination with other technologies, based on the likely effectiveness, implementability, and cost of this technology. However, NR and ENR are not retained for use in the Former Operations Area of the Site for assembly of alternatives, based on the limited effectiveness of this technology in the Former Operations Area Site setting.
4.2.3 Capping Capping comprises a variety of methods of encapsulating materials under an engineered cover. Generally, capping is the process of placing sand, sediments, soil, low permeability soil, or any variety of synthetic or composite engineered fabrics over impacted materials to mitigate potential risk posed by direct contact to the impacted solid material. Capping may be either over in-situ materials or excavated and placed materials. A cap provides a physical barrier, physical stabilization, erosion protection, and chemical isolation to reduce exposure to COIs (EPA, 2005). A low permeability cap can be used with or without a liner to reduce infiltration and leachate generation.
Capping, as applied to the Former Operations Area of the Site, may be either in-situ or in a designed consolidation cell. Capping is a well-established technology and is used for a variety of solid waste and mono-fill applications.
Capping, as applied to the Estuary Site, generally consists of natural granular material including clean sediment, sand or gravel. Sediment caps may also be constructed of synthetic materials including geotextiles, liners, and reactive or absorptive media. A cap may consist of multiple layers for optimal functionality (ASCE, 2007). When choosing capping materials, the following four main factors are considered: physical and chemical compatibility with the existing sediment, geotechnical compatibility, placement methods, and performance objectives.
Sediment capping can be implemented as a sole technology, or in conjunction with other technologies. To minimize cap disturbance and prevent future human or ecological exposure to the COIs, institutional or engineering controls are often employed, which may include restrictions on access and future dredging.
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4.2.3.1 Applicability to the Former Operations Area of the Site The primary risk factors for Former Operations Area soil and sediments are direct exposure and the potential for movement into the estuary. Capping is an acceptable method to control direct exposure to contaminated materials and prevent erosion of the capped material.
The main limitations of capping in Former Operations areas include:
x Water courses are subject to wide variations in flow due to storm events potentially requiring armoring or other methods to control erosion.
x Capping in the Former Operations areas will be designed with consideration of potential development opportunities.
x COIs are left on site, so restrictions to site use, monitoring, and maintenance are needed to ensure the cap is not disturbed and remains an effective barrier.
x Caps may alter conditions in the stream or wetland flow patterns, and habitat.
4.2.3.2 Applicability to the Estuary Site COIs at the Estuary Site are low in solubility and mobility, which makes a granular cap an effective means of preventing exposure to COIs by potential receptors. The MPCA has identified potentially bioactive zone (BAZ) thicknesses that need to be considered at the Site when evaluating capping. These thicknesses (50 cm to 120 cm) are based on habitat zone, water depth and substrate that must remain below the sediment PRGs listed in Section 3 following remedy implementation (MPCA, 2014b). These capping thicknesses could be met in various areas of the estuary, either alone, or in some shallow locations removal would need to precede cap placement so that the necessary cap thickness may be placed while still maintaining an acceptable water depth for the desired habitat.
As described in the CSMs in Section 2, the hydrodynamic conditions at the Site are relatively stable with limited potential for sediment transport in the Wire Mill Delta due to the protection from wind-driven waves, and little to no sediment transport observed in Unnamed Creek Delta due to wave action effects being primarily in the foreshore. Cap erosion under such conditions is not a significant concern compared to high velocity flow conditions that exist in many river systems.
Sediment capping has the following advantages over other remedial approaches (EPA, 2005):
x It immediately reduces exposure to COIs and provides a clean substrate at the sediment surface for benthic recolonization.
x It is less disruptive and less expensive than sediment removal because it does not require material dewatering and disposal.
x Resuspension of impacted sediment is less likely during cap placement than during sediment removal.
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The main limitations of sediment capping include the following:
x COIs are left in place, so restrictions to site use, monitoring, and maintenance may be needed to ensure the cap is not disturbed and remains an effective barrier.
x Caps may alter conditions in the water body such as navigation depths, flow patterns, and habitat.
4.2.3.3 Screening Effectiveness. Capping has the potential to significantly reduce long term exposure pathways from impacted sediments at the Site, by isolating impacts from potential receptors. Short-term impacts from capping may include transient movement of porewater from impacted sediment into the cap during placement. An effective cap material, thickness, and maintenance program can be selected to meet the Former Operations Area and estuary remediation goals and prevent future erosion. Capping is considered a highly effective technology for both the Former Operations and Estuary Sites.
Implementability. Caps can be installed with standard construction and remediation equipment. Depending on proposed water depth and habitat zone, temporary or permanent surface water diversion may be needed during construction. Capping is considered more easily implemented than sediment removal and disposal, but less easily implemented than institutional controls alone. Capping in the estuary will require resuspension controls. Depending on proposed water depth and habitat zone, some dredging may also be needed to accommodate the required cap thickness. Erosion and maintenance of a cap at the Estuary Site would be manageable considering the relatively stable hydrodynamic conditions. For both the Former Operations Area and the Estuary, capping is considered more easily implemented than sediment removal and disposal, but less easily implemented than natural recovery or institutional controls alone. The treatability study (EA, 2014) and geotechnical evaluations (AECOM, 2014 and Barr, 2014c) indicate that capping is a feasible remedial element.
Relative Cost. Costs for capping are dependent on cap thickness, materials, and surface water engineering factors. Relative costs for capping are considered moderate; less than for sediment removal and disposal, but significantly more than natural recovery or institutional controls.
4.2.3.4 Screening Results Capping is retained for assembly of alternatives based on the likely effectiveness, implementability, and cost of this technology for both the Former Operations and Estuary Sites.
4.2.4 Excavation and Removal Excavation can be used to remove soil from Former Operations areas and sediment from a stream channel or wetland. Excavation is a proven technology for removing impacted soil and sediment. For the Former Operations Site, sediment removal would consist of mechanical excavation using standard construction equipment. Control measures such as containment barriers, stream diversion, and cofferdams would be used to minimize sediment migration and control stream flow during excavation activities. Excavation would require dewatering and disposal of the removed sediment (EPA, 2005). Some key considerations for
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excavation include the assessment of the physical environment (e.g., storm water flow, surface water diversion or damming, and habitat alteration).
Dredging would be used to remove sediments from the Estuary Site. Dredging is a proven technology for removing impacted sediments. Sediment removal can be completed using a hydraulic dredge, or mechanically, using excavation equipment. Dredging can be completed while sediment is submerged (wet) or when water is removed from the dredging area (dry). Control measures such as silt curtains, air bubble curtains, or containment barriers would be used to minimize sediment migration during dredging activities. Dredging is frequently paired with a residual cover or NR to manage dredge residuals that will remain after dredging (USACE, 2008) and typically requires dewatering and disposal of the removed sediment (EPA, 2005). Some key considerations for dredging include the assessment of the physical environment (e.g., bathymetry, sediment materials, presence of debris or hard pan, and depth), resuspension controls, required dredging accuracy, waterway uses and infrastructure, and habitat alteration.
Mechanical dredging of wet sediments removes sediment through mechanical force, typically an excavator or crane equipped with a traditional or environmental bucket placed on a working barge. Sediment is lifted to the surface with approximately the same moisture content as in situ material and placed on a transport barge. Mechanical dredging is often needed for the removal of large debris, cemented material, or in tighter spaces, where access with hydraulic dredge equipment and associated pipelines may be difficult. Mechanical dredging typically results in higher sediment resuspension rates than hydraulic dredging, although environmental dredge buckets can be used to reduce resuspension (ITRC, 2014).
Mechanical removal of sediments can also be completed under dry conditions, after water has been diverted or drained from the removal area following construction of a containment barrier such as a cofferdam. Typically this technology is limited to shallow areas and smaller sized projects. Dry removal has been used successfully on a number of projects and greatly reduces the potential for resuspension of sediment when compared to wet dredging. Dry removal allows for visual inspection of the work area, use of more traditional excavating equipment, and less sediment dewatering than wet dredging. However, there have been issues with dewatering the sediment enough to effectively excavate and handle the material at a number of sites.
Hydraulic dredging removes and transports sediment in the form of a slurry using large volumes of water in the process. Slurries from hydraulic dredging therefore have higher water content than mechanically dredged sediments, requiring more space and time for dewatering and water management. Many types of hydraulic dredging equipment are available, and are selected to meet site-specific needs, sediment characteristics, transportation requirements, accuracy levels, removal depths and production rates, with cutterhead equipment being the most commonly used (EPA, 1994 and 2005). Hydraulic dredging equipment can typically achieve overall higher production rates than mechanical dredging, especially when used to dredge very large volumes of sediment (EPA, 1994). Hydraulic dredging is also beneficial over mechanical methods in cases where the dredged sediment needs to be transported a large distance to the disposal site.
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Advantages to sediment removal over other remedial technologies include:
x COIs are removed, reducing the uncertainty associated with long term effectiveness.
x Removal of COIs allows for more flexibility and fewer restrictions for future betterment or redevelopment activities compared to capping or NR, which require monitoring and management.
General disadvantages of sediment removal include:
x Mobilization of previously contained COIs may occur, resulting in impacts to the water column and remobilization and deposition of COI-impacted sediment in previously clean areas.
x Management and disposal of sediment is necessary; requiring dewatering, a disposal site and transportation, which add complexity, cost, and duration to a project compared to in-situ treatments such as NR or capping. Hydraulic dredging can generate a large quantity of water that may create a bottleneck in the on-shore processes (depending on the availability of drying and staging areas) that can cause significant delays and require permitting and treatment prior to discharge.
x Disruption to the site is significantly greater than for in-situ technologies because of sediment removal, handling and disposal requirements.
x Disruption of the wetland or stream environment is unavoidable during excavation.
x A residual sediment cover is generally required because it is not technically feasible to remove all sediment without some quantity of residual remaining.
4.2.4.1 Applicability to the Former Operations Area Site Complete or partial excavation could be one component of the remedial alternatives for the Former Operations Area. It may also be combined with capping, where sediment is removed to a set elevation to achieve a specified barrier thickness, topographic slope or other physical need.
Selection of the most appropriate excavation method would depend on the size of the area to be excavated, the final disposal method of removed sediments, and geotechnical considerations for the final stream channel or wetland. A residual cover may be needed in some areas to manage residuals that may remain after excavation.
4.2.4.2 Applicability to the Estuary Site Sediment removal could be one component of the remedy used for the Estuary Site sediments. Removal would also allow for adequate depths for capping to meet the required potential BAZ thicknesses in some areas of the Estuary Site (MPCA, 2014b).
Sediment resuspension control measures would be needed to control mobilization of COIs during dredging, based on dredging elutriate testing results (EA, 2014). Mechanical dredges typically limit
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resuspension of fines and contaminants from sandy sediments, while hydraulic (cutterhead and plain suction dredges) limit resuspension of very soft, fluid sediments (ITRC, 2014). Estuary Site sediments are soft, so proper selection of dredging equipment and control measures would be needed (EPA, 1994 and 2005).
Selection of the most appropriate sediment removal method for the Site will require further assessment of site-specific conditions, including the physical characteristics of the sediment bed, time and space available for sediment and water management, the volume of sediments that would be removed and the feasible disposal options. Based on these aspects, mechanical removal, under wet or dry conditions, may be more applicable for sediment removal from the Estuary Site for the following reasons:
x Large debris in areas of the Wire Mill Delta, and cemented non-native sediment layers in Unnamed Creek Delta may require removal using mechanical methods. If hydraulic dredging is used at the Estuary Site, it would likely require removal of debris prior to dredging and would only be implementable to areas that do not have cemented sediments.
x Mechanical removal may require less water management than hydraulic dredging, reducing the water treatment costs and space required for sediment management and disposal.
x Efficiencies gained from hydraulic methods versus mechanical methods may not be realized for this Site because of the moderate volume of sediments anticipated for removal. However, the dredging type applicable for the Site will be evaluated during design.
x Hydraulic dredging is generally beneficial over mechanical methods when sediments are transported a large distance through a pipeline to the disposal site, since there is less material handling and transportation required. This is not the case for this Site, because the potential dredged sediment disposal areas being considered are relatively close to the removal areas.
x Mechanical removal in dry conditions may be implementable in some areas of the Site, including the Unnamed Creek Delta, where the geometry and shallow depth of the delta allows for construction of a containment barrier and diversion of water.
x Sediment resuspension control measures will likely be needed to control mobilization of COIs during dredging, based on dredging elutriate testing results (EA, 2014).
x A residual cover may be needed in some sediment removal areas to manage dredge residuals that may remain after dredging.
4.2.4.3 Screening Effectiveness: Excavation and removal is considered a proven and effective method for removing impacted soil from Former Operations areas and sediment from wetland, stream channels areas, and the estuary for subsequent management and disposal. Removal will achieve the Former Operations Area and Estuary RAOs.
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Implementability: Excavation and removal can be implemented in both the Former Operations Area and Estuary Sites. Excavation at the Site is implementable using standard civil engineering methods and controls. Contractors are available with the equipment and expertise to work with the types of materials expected in the Site. However, excavation in wetland areas would require permitting. Dry removal of sediments may be feasible in portions of the Unnamed Creek Delta, where the construction of a containment barrier and water diversion could be implemented. In open water portions of the Estuary, dredging in wet conditions is considered to be implementable at the Site. This work would require specialized equipment and skilled dredge operators. Significant permitting would be necessary to implement sediment removal. Soil and sediment removal could cause significant short-term disruption to the Site and would require erosion control measures in Former Operations areas, resuspension control management, sediment handling, and dewatering activities. Hydraulic dredging alone is not considered feasible at the Site due to the presence of debris and cemented non-native sediments. Overall, excavation and removal are more difficult to implement than all other non-invasive technologies.
Relative Cost. In general, excavation and removal costs are significantly higher than response actions where soil or sediment is managed in place due to the subsequent costs associated with sediment management and dewatering, water treatment, transportation, and disposal. At this Site, costs for mechanical dredging would likely be less than hydraulic dredging because mechanical methods would also need to be employed to remove debris and cemented sediment, and the disposal space and water treatment requirements are less with mechanical means compared to hydraulic dredging.
4.2.4.4 Screening Results Excavation and removal, including mechanical and hydraulic removal of sediments under both wet and dry conditions, is retained for assembly of alternatives for the Site, as these methods would be effective at meeting Site RAOs.
Management and disposal of sediment and water is necessary following removal of sediments from wet areas. These steps generally include dewatering, transport to a disposal site, material handling and placement at the final disposal site. The sequence and methods used for sediment management will depend highly on the removal method and the disposal site location and design.
4.2.5 Sediment Containment and Disposal Containment of soils and sediments may occur at an offsite location such as an existing permitted landfill or at a facility constructed onsite.
Off-site containment (i.e., disposal) involves transporting soil or sediment to an existing off-site disposal location. Removal, dewatering, and applying reagents to bind any free-liquids, as necessary, are generally the only actions required before transport and disposal at most landfills. Truck traffic volume at the Site and surrounding community may be disruptive, and could create noise and emission concerns or damage to existing roads. Temporary roadways are often constructed onsite specifically for sediment transport.
On-site disposal can be accomplished in different areas relative to the water body—in upland or near-shore area or sub-aqueously in the estuary. An on-site containment area may have different engineering
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requirements based on the choice of location and the nature of the material that is placed, and ultimately managed, in the containment system.
Consolidation with a simple cap may be used for materials that are relatively immobile and where direct contact is the primary mode for potential exposure. More complex engineered structures may be needed where water management is likely to be required over a longer duration or where slope stability needs to be considered, due to the height of the consolidation material. For example, consolidation of removed materials along the upland portion of the existing spit-of-land could take advantage of the existing geography and shallow depths to reduce construction and water management needed.
Confined Disposal Facilities (CDFs) are a widely used disposal technology for impacted sediments from both navigation dredging and remediation projects (EPA, 1994). The goal of confined disposal is to physically isolate and contain excavated sediments. Because of the nature of excavated sediment, a CDF must be designed to provide for placement of sediments and treatment of the effluent water. For example, hydraulically dredged material has higher water content than mechanically dredged material, and may take much longer to dewater before a CDF can be covered and closed. Design of a CDF requires detailed knowledge of the characteristics and quantity of impacted sediments. The CDF design must result in a stable structure, considering the geotechnical properties of the sediment. Effluent from sediment placement often requires treatment. Leachate and runoff must also be assessed and potentially managed.
Confined aquatic disposal facilities (CADs) are used to place and cap materials in a natural or excavated depression under the water, providing containment of the material. Design of a CAD facility requires detailed knowledge of the quantity and type of impacted sediments as well as hydraulic conditions. CAD areas may require a monitoring program to ensure COIs are effectively immobilized and have similar limitations as conventional sediment caps (Section 4.3.3). Materials used for construction should also prevent lateral migration.
4.2.5.1 Applicability to the Former Operations Area of the Site Areas are available at the Site to accommodate a CDF for the estimated volumes of sediment being considered for removal from the Former Operations Site areas and the estuary. The CDF could be a repository located solely in an Former Operations area, or may cover both Former Operations are and near-shore shallow estuary zones.
4.2.5.2 Applicability to the Estuary Site Areas are available in the Estuary Site to accommodate a CAD for a portion of the estimated volumes of sediment being considered for removal. These locations include the water intake hole in the Wire Mill Delta and the dredged channel in the Unnamed Creek Delta habitat.
4.2.5.3 Screening Effectiveness. On-site or off-site disposal of Site sediments would be effective at achieving remediation goals since the sediments would be removed. An on-site CDF located in an Former Operations Area or near-shore area could effectively mitigate human and ecological exposure to COIs if designed to
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appropriately contain COIs. Wastewater created during the dewatering process would likely require treatment.
Implementability. Construction of a CDF would cause short-term disruption at the Site and would create permanent structures that would require long-term maintenance and monitoring. Although subaqueous disposal in a CAD in a natural depression would create less Site disruption and would have lower relative costs than a CDF, an existing, suitable location for a CAD that could accommodate the anticipated removal volumes without impacting fish habitat is not available in the estuary. Dredging to form a CAD is also not considered to be cost effective. Off-site disposal is implementable, given the Site is generally accessible for off-site transportation of sediments, but truck traffic would cause disruption to the Site and surrounding community and additional dewatering would be required prior to off-site transport. A potential benefit to locating a CDF on-site and in a near shore area would be the ability to place it over impacted sediments, thereby reducing the volume of sediments and water required to be removed, managed, and transported to another location. A preliminary evaluation of geotechnical and treatability considerations associated with construction of an on-site CDF was also conducted (AECOM, 2014 and Barr, 2014c). Both studies supported the conclusion that CDF construction was implementable as a remedial technology. Placement of a CDF in a near-shore area may require additional consideration of storm water controls.
Relative Cost. Relative costs for containment and disposal depend highly on the volume of sediment to be managed as well as the proximity of the disposal site relative to the removal area. In general, off-site disposal is more costly than on-site due to the cost of transportation, disposal fees, and significant material dewatering and handling. However, landfill costs may be off-set by construction costs for on-site disposal areas depending on site constraints. Cost for components of an onsite CDF/containment area, or repository can be substantial, and may include design, sediment dewatering, construction equipment, construction materials, containment structures (berms), and operation of a water treatment system for the effluent from sediment dewatering.
4.2.5.4 Screening Results On-site disposal in a CDF is retained for the assembly of alternatives for the Site. Feasible disposal site locations could include an upland repository in the Former Operations Area, or areas above existing sediments, provided storm water can be properly managed.
On-site disposal in a CAD is not retained for the assembly of alternatives for the Site because of the limited volume available for disposal underwater and the loss of fish habitat that would result from placing a CAD in water intake hole in the Wire Mill Delta and the dredged channel in the Unnamed Creek Delta.
With the exception of elevated lead levels in dredge spoils within OU-Q, off-site disposal is not retained for the assembly of alternatives for the Site because of the additional handling, transportation and disposal costs and Site and community disruption.
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4.2.6 In-Situ Treatment In-situ treatment of sediments currently is less common than in-situ treatment of soils because these methods are much more difficult to implement and monitor in subaqueous environments. However, recently the effectiveness and implementability of some subaqueous in-situ remedies (especially use of activated carbon) have been demonstrated. In-situ treatments typically result in less disruption to the site when compared to excavation or removal and may be completed within a shorter time frame in comparison to natural recovery. The following in-situ treatment technologies were reviewed for consideration in the assembly of alternatives for the Site:
x Immobilization
x Enhanced Bioremediation
x Oxidation/Reduction
x Chemical Oxidation
x Phytoremediation
x Adsorption
Immobilization: In-situ immobilization treatments involve the addition of chemicals and/or solidification products to bind with impacted materials and reduce the leachability of COIs. Immobilization can be achieved by two mechanisms: solidification or stabilization. Solidification encapsulates impacted sediments to form a solid material restricting COI migration by decreasing the amount of surface area available for leaching. Stabilization is a process which involves chemical or adsorbtive reactions to convert COIs into less soluble, less mobile, and less toxic forms and may change the physical characteristics of the COIs.
Enhanced bioremediation uses microorganisms, either native to the site or introduced, to degrade organic contaminants. Nutrients, oxygen, or other amendments may be added to accelerate the process.
Oxidation/reduction is the addition of chemicals capable of serving as an oxidant or electron acceptor to facilitate aerobic decomposition.
Chemical oxidation involves the use of chemical additives to transform, degrade, or immobilize organic contaminants. Common oxidizing agents include ozone, hydrogen peroxide and permanganate.
Phytoremediation uses trees, grasses, or high-biomass crop species to remove, transfer, stabilize, or destroy COIs.
Adsorption. As with ex situ treatment of water, adsorbents can also be used as sediment amendments for in-situ treatment of COIs. It is possible for sorption of metals and organics to take place simultaneously with a suitable combination of sorbents, such as adding ion exchange materials to activated carbon. However, it is unknown if amendments would affect activated carbon’s sorption capacity.
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4.2.6.1 Applicability to the Former Operations Area of the Site As a requirement of the MPCA ROD for the Site, research into innovative and alternative treatment methods for Former Operations Area (and estuary) sediments was conducted and submitted to the MPCA (Barr, 1990). The results of this work showed that in situ treatments, especially bioremediation, had limited potential for success at the Site given the concentrations of the COIs and the physical nature and subaqueous setting of the materials.
Physical in-situ treatment, solidification and stabilization, was used to treat Former Operations Area sediments within the Unnamed Creek channel (Geraghty & Miller, 1996). The soil and sediment within a portion of the channel (referred to as Operable Unit J) was successfully stabilized in-situ and subsequent monitoring of this area suggests that this work was effective at immobilizing the COIs present within this former operable unit. While this work was effective, completing this remedial effort required overcoming several challenges including the restrictions to storm water and the consistency of the stabilized mixture. The stabilized material met both structural and hydraulic conductivity specifications.
4.2.6.2 Applicability to the Estuary Site Until recently, in-situ treatment options had been considered less proven in the estuary environment but recent advancements in the use of activated carbon at sediment sites have shown promise. In-situ technologies tend to work best in well-controlled areas, where the treatment materials can be introduced to the impacted sediment in doses sufficient to cause the desired effect. Challenges to implementing in-situ treatments at the Estuary Site based on site-specific conditions include:
x Uncertainty due to difficulty with delivering the appropriate quantity and distribution of chemicals or amendments to the treatment zones.
x Addition of chemicals may alter the habitat or be toxic to benthic and aquatic organisms in the estuary.
x The physical characteristics of the sediments not supporting biological technologies.
4.2.6.3 Screening Effectiveness: Site-specific treatability testing would be needed to determine whether in situ treatment could be feasible at locations on the site other than those where this technology has already been implemented. The previously completed in-situ treatment in the Former Operations Area of the Site resulted in a modification of the surface water system in the Unnamed Creek and therefore, evaluation of the potential effects would need to be evaluated. There are limited areas in the Estuary Site where physical conditions would allow enough control of the in-situ treatment material application to effectively remediate impacted sediment
Implementability: In-situ treatment has been successful implemented on the Former Operations Area Site and could be used with additional evaluation and treatment testing of the proposed soil or sediment. The implementability of in-situ treatment options for Estuary Site sediments is considered low because
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adequate distribution of the treatment media to the appropriate location is difficult in a dynamic estuarine environment.
Relative Cost: The cost for in-situ treatment options may be higher than those for conventional capping or removal, depending on the type and quantity of chemicals or amendments required for treatment and possibility of reapplication(s). While in-situ treatment could be less costly than removal in some applications, the lower certainty regarding effectiveness and implementability of application and the possibility that additional technologies may be needed to meet RAOs, reduces the feasibility of this technology, especially for the Estuary Site.
4.2.6.4 Screening Results Given the uncertainty of application success and the potentially greater cost compared to capping or removal and consolidation, in-situ treatment was not considered for further evaluation in the Estuary Site. In-situ treatment may be further evaluated for application in the Former Operations Area of the Site.
4.3 Water Management Technologies Water will need to be managed with both the Former Operations Area and estuary sediment management activities. Technologies for management of water that are considered in this screening evaluation include:
x Surface Water Engineering
x Water Management
The technology and process screening results for water management technologies are summarized in Table 4-2. Technologies and process options deemed most favorable were retained for assembling the alternatives described in Section 5.
4.3.1 Surface Water Engineering Surface water engineering comprises a broad group of approaches to manage the flow of surface water. Surface water engineering would be combined with one or more remedial technologies as part of an overall remedy to either remove or physically stabilize impacted sediments. Due to the relatively wide range of storm water flows, particularly in the Unnamed Creek, some manner of surface water engineering is necessary for a successful Project. The surface water engineering technologies that could be used include:
x Stream Channelization: This would include regrading the Unnamed Creek stream channel to direct flow away from contaminated areas, and to control sediment transport; using features similar to a natural stream channel. Stream channelization may also include liner materials and geotextiles for sediment control;
x Stream Culverting: This engineering approach would include installing a culvert pipe or other engineered structure to carry water over or through a contaminated area; and
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x Stream Diversion: This approach would include relocating all or a portion of the stream channel away from a contaminated area.
Surface water engineering offers the following advantages compared to the current Site conditions:
x Allows for a range of consolidation and capping remedies to be considered;
x Can minimize dewatering during excavation;
x Allows for potential future habitat/scenic value improvement (betterment); and
x May be used to improve site hydraulics and minimize erosion.
The main limitations of surface water engineering in Former Operations areas include the following:
x Former Operations Area water courses are subject to wide variations in flow due to storm events requiring potentially larger structures which result in more effort for work sequencing and contingency during construction;
x A high level of short term disturbance is required to the flow system during construction; and
x The methods require modifications to existing flow patterns and habitat.
While it is not possible to move the entire watershed, it may be possible to consider up-gradient diversions that could limit the volume of water that would need to be conveyed through the Unnamed Creek channel over the long-term. An up-stream approach to managing water could minimize the potential for scour or erosion during future storm events and would provide a more stable remedy for the long-term.
4.3.1.1 Applicability to the Site Due to the presence of active stream courses at the Site, some degree of surface water engineering will be necessary for all but the no action alternative.
4.3.1.2 Screening Effectiveness: Channels, culverts and diversions are well established tools of civil engineering and are highly effective in managing surface water flow and erosion.
Implementability. Channels, culverts and diversions are well established tools of civil engineering and are implementable using standard methods for both design and construction. Permitting is necessary for disturbing wetlands and modifying storm water flows.
Relative Cost. Costs are highly design specific for any type of surface water engineering.
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4.3.1.3 Screening Results Surface water engineering is retained for assembly of alternatives based on the likely effectiveness, implementability, and cost of this technology.
4.3.2 Water Management Dewatering technologies are typically needed to prepare excavated or dredged sediments for disposal. Dewatering simplifies handling and transportation and reduces the volume and weight of sediments, reducing disposal costs. Dewatering is expected to be a more significant requirement for the estuary sediments due to the setting and volume. Dewatering sediments reduces the capacity and area needed for an on-site disposal facility and improves material handling, stability and strength.
Dewatering processes applicable to excavated sediments include passive dewatering, reworking sediments, hygroscopic amendment addition, and mechanical dewatering methods. Passive dewatering relies on natural evaporation and drainage and requires construction of a staging area and time to implement the drying process. Due to the generally fine-grained nature of the sediments in both estuaries, passive dewatering would likely require supplementation with another dewatering process option. Preliminary testing of potential drying methods including Calciment and Portland cement have been completed and are described in more detail in Section 5 (EA, 2014).
Sediment reworking with mechanical equipment is often employed to promote drainage and enhance passive dewatering methods. Dewatering can also be enhanced by mixing dredged sediments with hygroscopic amendments to absorb the water and remove moisture. Use of amendments can also provide geotechnical benefits to a disposal area, for example, increasing strength and stability of the sediment. Mechanical equipment containing presses and plate filters can also be used to press or squeeze water from dredged sediments. Mechanical dewatering generally works best with a homogeneous waste stream and constant flow rate, so temporary storage in a tank, lagoon, or CDF would be necessary to equalize flows and concentrations prior to further dewatering by one of the mechanical processes (EPA, 1994). Use of mechanical dewatering methods would decrease the amount of time and size for a CDF, but involve additional costs for equipment, infrastructure and energy use.
Other dewatering methods are typically employed for sediments that are hydraulically dredged. These include rapid dewatering systems that use mechanical and polymer treatment, geotextile tubes with polymer treatment and gravity separation and dewatering. Because these processes are specifically applicable for hydraulic and not mechanical dredging methods, they will be considered further during design if hydraulic dredging is identified as a potential sediment removal method.
Water removed during sediment management and disposal processes typically require treatment prior to discharge to remove COIs in the wastewater stream and to meet other National Pollutant Discharge Effluent Standards (NPDES). Water treatment technologies can range from filtration to remove solids and use of absorptive media to remove dissolved phase contaminants to methods designed to target specific COIs such as bioreactors and advanced oxidation.
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4.3.2.1 Applicability to the Site Passive dewatering methods would be appropriate to use at an on-site disposal facility, but would likely require sediment mixing, reworking and/or hygroscopic amendment addition to facilitate timely and adequate dewatering given the fine-grained Estuary Site sediments. The specific dewatering method and type and amount (if any) of amendments required would be identified during a detailed design or refined during implementation.
Dewatering effluent will likely require treatment prior to discharge based on effluent elutriate test results (EA, 2014). Wastewater treatment processes applicable for the Site COIs may include use of flocculants or filtration to remove COIs sorbed on suspended solids, and/or liquid adsorption which uses an absorbent media to adsorb dissolved phase COIs from the wastewater stream. Bioreactors and advanced oxidation can be used to treat organics, but are not effective at removing metals.
4.3.2.2 Screening Effectiveness: Passive dewatering methods, combined with sediment reworking are deemed effective processes and applicable to the on-site disposal options being considered. Effective water treatment options are available to remove COIs from effluent water. The need for a water treatment system would be identified and the appropriate treatment equipment and media would be selected during detailed disposal facility design.
Implementability: The required dewatering and water treatment processes are highly implementable at the Site and could be performed within the space available, near or within an on-site disposal facility. Standard filtration and adsorption methods could be used for water treatment of the site COIs, requiring technical knowledge, but no highly specialized equipment.
Relative Cost: Costs for dewatering for on-site disposal are moderate relative to dewatering requirements for off-site disposal, as passive methods can be employed at the final disposal site and fluid reduction requirements are less stringent than for sediments that would be transported off-site. Costs for water treatment are relatively high, but depend on the treatment train and level of treatment required to meet discharge requirements.
4.3.2.3 Screening Results Process components for water management during on-site disposal that are retained for consideration include passive dewatering, sediment reworking and hygroscopic amendment addition, as well as treatment of wastewater.
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5.0 Alternatives Evaluation This section presents the assembled alternatives stemming from the technology screening and multiple discussions and input from various groups. The common remedial elements of the assembled alternatives are described along with habitat/recreational enhancement elements that have been incorporated into the alternatives. The habitat enhancement elements are based on the AOC habitat goals, and resource managers input, including an AOC habitat work group (SLR-CAC, 2002; LimnoTech, 2012), and GLNPO program expertise. In Fall 2014 eleven alternatives were assembled and taken through a screening evaluation that resulted in a score for each alternative. Based on the score of each alternative and additional Project considerations, four alternatives were retained for detailed evaluation. The detailed evaluation of the four alternatives resulted in the identification of a preferred alternative. The Draft FS was completed and submitted to resource managers and the MPCA in November 2014. U.S. EPA began tribal consultations under Section 106 of the National Historic Preservation Act (NHPA) in March 2015 during which the draft FS was discussed. In light of the tribal consultations and discussions with MPCA, a twelfth alternative was assembled and included in an updated alternatives screening and detailed analysis. The following sections further describe the updated alternatives evaluation process.
5.1 Development of Alternatives Based on the technology screening discussed in Section 4.0 and the PRGs provided by the MPCA in its March 5, 2014 letter, preliminary alternatives were developed. These alternatives were further refined through discussions with the Project partners (GLNPO, MPCA and U. S. Steel) and through a series of meetings and discussions that are briefly summarized below.
5.1.1 Review and Input on Alternatives Development The MPCA presented early descriptions of potential alternatives or remedial elements to the resource managers and the AOC habitat work group over the course of multiple briefings. The initial briefings included discussions of much of the information presented in Sections 4.0 and 5.0. A meeting of the members of the AOC habitat work group and resource managers was convened in March 2014 at the Duluth MPCA office. MPCA facilitated a day-long discussion of Site conditions and remedial elements, and the Project partners were given specific input on preferences regarding remedial strategies and habitat goals for the Spirit Lake estuary area from estuary habitat management stakeholders (LimnoTech, 2012). During the subsequent months, the MPCA Project staff also met with resource managers, tribal representatives, City of Duluth staff and neighborhood representatives. Through these additional interactions, further feedback was provided on elements of Former Operations Area and estuary sediment remediation to help develop a selection of remedial options for evaluation in the draft FS (Barr, 2014d).
As noted above, the draft FS was produced in November 2014 (Barr, 2014d). A meeting of resource managers, tribal resource management staff, USS, MPCA and U.S. EPA occurred on November 18, 2014. Comments were received from the MPCA, resource managers, City of Duluth, St Louis River Alliance representative, and the Fond du Lac band staff. The Tribal Consultation with U.S. EPA began in March 2015 and in late May these consultations, together with discussions with MPCA resulted in development
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of a twelfth alternative, which is included in the screening and detailed alternatives evaluation that follows in this updated FS.
Based on the input received and taking into account MPCA and GLNPO programmatic requirements, a range of twelve alternatives were developed.
5.2 Common Remedy Elements The following subsections describe common remedy elements for the Site that are included in many of the alternatives described in Section 5.4. Appendix I provides schematic illustrations of the remedy elements discussed throughout this Section.
5.2.1 Institutional Controls Institutional controls layered over engineering controls will address the future threat of disturbance to protective measures associated with Site remedies. Institutional controls will be specific to a given remedial alternative and will consider potential long- and short-term controls. Institutional controls may include an environmental restrictive covenant for portions of the Site with private property ownership. For areas that are not private property, other institutional controls by the various local, state and federal permitting agencies could be implemented to restrict various activities (e.g., dredging) as conditions of future permits.
5.2.2 Natural Recovery Natural deposition of new sediment layers over impacted sediments has been observed in the near shore and off shore zones of the Estuary Site. Areas that are within the PRG footprint, but do not have a remedy element shown are natural recovery (NR) zones. These areas have sufficient cover material and meet the RAOs and based on hydrodynamic modeling, site observations, geologic stratigraphy, and multiple bathymetric surveys, are expected to be stable and will therefore be protective over time. The NR areas will be monitored to confirm the sediment cover layers remain in place.
5.2.3 ENR Thin Cover The enhanced natural recovery (ENR) thin cover will be placed in areas where the water depth is greater than 3 feet and the non-native sediments exhibit COI concentrations that exceed the PRGs, but are thin deposits (generally 15 cm/6 inches or less) with COI concentrations generally less than the level II SQT for the respective COIs. This element is applied where the setting and hydrodynamic conditions are shown to be stable similar to the factors noted in Section 5.2.2. Appendix I, Figure I-1 shows a schematic of the ENR thin cover concept.
5.2.4 Remedial Capping 5.2.4.1 Former Operations Area Remedial capping of non-native Former Operations Area sediments involves placing a two-foot soil cover over areas where non-native soil or sediments will be managed in place. The bottom 1.5 feet will be comprised of a borrow layer and the top 6 inches will be topsoil. The capped areas will be vegetated with
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shallow rooted grasses, and woody vegetation and animals will be managed to maintain the cap integrity and maintain protectiveness. The CDA cap will include a geomembrane layer overlain by the two-foot soil cover. Several of the remediation alternatives include remedial capping of OU-I sediments similar to the estuary capping and is comprised of a 0.5 m (1.64 ft) cap with root barrier and possibly rip-rap. This setting requires the use of root barrier, where woody vegetation such as willows may colonize shallow water areas and the potential exists for burrowing animals to be present. In such settings, the barrier layer design may need to consider less deep burial to help prevent excessive colonization by burrowing vertebrates or deep rooting plants that may result in excessive disturbance of the overlying cap material. This aspect will be evaluated further during remedial design. Appendix I, Figures I-2 and I-3 shows schematic cap cross sections.
5.2.4.2 Estuary Remedial capping in the estuary areas involves placing granular materials to meet the specified thickness requirements. As detailed in the MPCA letter, the remedial cap thickness would be based upon the post remedy habitat type. To develop these alternatives, post remedy habitat type was defined based on water depth and proximity to shore. The water depths that have been selected for each remedial cap thickness are listed below. If present, the existing sediments that have COI concentrations less than the MPCA PRGs are considered as part of the overall remedial cap thickness. The overall cap thickness would consist of the potentially BAZ thickness presented in the MPCA letter and an isolation zone (IZ), if necessary, which would be determined during design of the selected alternative. Appendix I, Figures I-4 through I-6 show schematic cross sections illustrating the remedial cap with potentially BAZ thickness and underlying isolation zone for the different settings or configurations listed below.
Estuary remedial cap thicknesses
x In estuary shoreline zone (as defined in Section 2.0): 1.2 meter (m) (3.93 ft) cap thickness
x 0 to 3 feet water depth that is adjacent to shoreline: 1.0 m (3.28 ft) cap thickness, or
x 0 to 3 feet water depth that is adjacent to shoreline: 0.5 m (1.64 ft) cap with root barrier, where necessary, to preserve water depth for armoring, to prevent deep rooting by plants, or to prevent animal burrowing.
x >3 feet water depth or <3 feet water depth and not adjacent to shoreline with low potential to shoal or transition to emergent habitat: 0.5 m (1.64 ft) cap
5.2.5 Removal to a Set Elevation and Cap Placement An approach involving removal to a set elevation will be used in areas where the extent of removal does not encompass the full vertical extent of sediment with concentrations greater than the PRGs. A remedial cap will be placed following removal to a set elevation. Appendix I, Figure I-7, shows a schematic of the removal to a set elevation and remedial cap material placement to the required potentially BAZ thickness with underlying isolation zone for areas of the Site where this is the selected remedy element.
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5.2.6 Removal to PRGs An approach involving removal to the PRGs will be used in areas in which the extent of removal encompasses the full vertical extent of sediment with concentrations greater than the PRGs. A dredge residual cover will be placed following the removal to manage dredge residuals. Appendix I, Figure I-7 shows a schematic of this removal and residual cover placement remedy element.
5.2.7 Dredge Residual Cover A dredge residual cover will be placed over areas where removal thickness targets the entire vertical extent of sediment with concentrations greater than the PRGs. The residual cover layer will be placed after dredging is completed to manage dredge residuals and will be constructed with characteristics such as grain size to account for the energy regime, habitat type and other conditions affecting the setting of the location within the selected alternative. As noted above, placement of a dredge residual cover is illustrated schematically in Appendix I, Figure I-7.
5.2.8 CDF Confined disposal facilities (CDFs) are part of several alternatives and include several elements, such as perimeter berms, internal drainage systems, perimeter toe drains, storm water management of the cap, and the CDF cover system. The cover system will consist of a two-foot soil cap in which the bottom foot of this cover will consist of a low permeability barrier layer and the top foot will be comprised of 6 inches of borrow cover overlain by 6 inches of topsoil. While conceptually considered as part of the alternatives analysis, a CDF operations and maintenance plan and associated costs will be developed during the remedial design phase. Appendix I, Figure I-8 shows a schematic of the CDF cap and I-9 shows a schematic of the CDF perimeter berm. The height and configuration of CDF perimeter berms varies depending on many site factors as well as the design capacity; general information about likely berm height is discussed as an element of the assembled alternatives in Section 5.4.
5.2.9 Former Operations Area (Upland) CDF A CDF that will be placed in an upland location is part of three alternative remedies. The upland CDF will have similar elements as the estuary/Unnamed Creek area CDFs, with the addition of a three-foot base liner system. The bottom 2-feet of the base liner system will be comprised of a two-foot low permeability barrier layer. The top foot will consist of a sand drainage layer. A geomembrane will be placed on top of the low permeability barrier layer and below the sand drainage layer. The upland CDF cover system will be comprised of a two-foot soil cap, similar to the estuary CDF cover system. While conceptually considered as part of the alternatives analysis, an upland CDF operations and maintenance plan and costs will be developed during the remedial design phase if necessary. Appendix I, Figure I-8 shows a schematic of the upland CDF cap and Figure I-10 shows a schematic of the upland CDF liner system.
5.2.10 Storm Water Conveyance – Unnamed Creek Storm water conveyance through the Unnamed Creek channel, Unnamed Pond and Wire Mill pond areas presents a design challenge common to all active remediation alternatives, except for Alternative 11 where sediment removal provides added volume for storm water conveyance. Consolidation of non-
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native industrial sediment within the Unnamed Creek conveyance system will require rerouting and armoring of the current flow channel and reconstructing a flow management structure and embankment to manage storm water entering this Site feature from the larger upstream watershed. Unnamed Creek has two primary means of managing the storm water associated with all active remediation alternatives: (1) is to discharge to the OU-M delta; and (2) is to discharge to the depressed area of the estuary known as the Wire Mill Intake Area, east of the Spit of Land. Discharging to the OU-M delta will be comprised of open channel flow routed through the Unnamed Creek. Discharge to the Wire Mill Intake Area would only occur in alternatives where capping only of Former Operations Area sediment occurs or a CDF covers the OU-M delta. Discharge under these scenarios will consist of a combination of open channel flow and pipe flow. The storm water piping system will convey flow from the open channel underneath the existing railroad grade and discharge into the Wire Mill Intake Area below the water surface elevation. A rip-rap lined conveyance channel is common in many of the alternative remedies to route flow through the Unnamed Creek. The channel section will be sized to convey flows up to the 25-year 24-hour storm event. With the exception of Alternative 7, the existing weir structure at the downstream end of OU-I will remain in place or be replaced with a structure with similar hydraulics. This will allow flow to closely mimic existing conditions. Due to consolidation of impacted materials within the Unnamed Creek corridor under Alternative 7, ponding/retainage of storm flows will not be possible and storm water conveyance will consist of open channel flow along the entire Unnamed Creek course. Where used, the existing weir structure will be evaluated for structural integrity during the remedial design phase.
5.2.11 Storm Water Conveyance – Wire Mill Pond and Unnamed Pond Though less complex, the need to accommodate storm water through the smaller Wire Mill Pond sub-watershed is a primary driver for choosing to excavate and remove the industrial sediments from this area and allow the landscape and storm water to revert to historic patterns. The Wire Mill Pond will receive overland flows from the west and convey the flow into the Estuary. Pond banks and slopes will be protected to minimize erosion.
The Unnamed Pond receives storm water from a small 14-acre sub-watershed. With the exception of Alternatives 1 and 2, remedial excavation will occur within this basin to remove COIs that exceed established PRGs. Final grading and turf establishment will follow excavation of impacted material.
Appendix I, Figures I-11 and I-12 provides schematic illustrations of the proposed storm water conveyances.
5.2.12 Surface Water Quality As stated in FS Section 2.2.2, U. S. Steel has been engaged in an on-going effort to monitor surface water quality within and adjacent to the Site. The data generated through this on-going effort has revealed surface water impacts that are isolated in occurrence, limited in magnitude and contained within the terrestrial portions of the Site. Impacted sediment isolation and/or removal actions described above will also have the beneficial outcome of improving surface water quality in the limited areas of impairment. As such, remedial actions that specifically target surface water quality are not considered in this FS. Long term surface water quality monitoring will continue after construction of the final remedy.
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5.2.13 Lead-Impacted Soil Portions of the lead-impacted soil identified within OU-Q dredge spoils and OU-P during subsurface investigation activities were identified as being characteristically hazardous. On-site chemical stabilization followed by off-site disposal will be conducted to address these soils in the OU-P/OU-Q area.
5.3 Common Habitat Elements Alternatives 5 through 8 and 12 include creation of new or deeper open water at the OU-M Delta/Unnamed Creek Delta area, which are consistent with the conceptual habitat plans for the lower St. Louis River (SLR-CAC, 2002) and Spirit Lake (LimnoTech, 2012). One primary difference between these four alternatives involves the restoration of open water in the OU-M delta where currently there is none. The depth of water in the resulting bay differs between some of these alternatives. To simplify descriptions of the alternatives, the definitions of two types of bays that may be envisioned are presented below. Details of each alternative are then presented in the following subsections.
5.3.1 Open Water Bay The open water bay water depths in the Unnamed Creek delta would be similar to the existing open water areas and would be approximately 1 to 2 feet deep. The bay will be created by removing sediment to a set elevation and remedial capping. Appendix I, Figure I-13 shows a schematic of the proposed open water bay and submerged shoal.
5.3.2 Shallow Sheltered Bay The open water depths created in the shallow sheltered bay of the Unnamed Creek delta will have average water depths ranging from 3 to 5 feet throughout most of the area. The bay will be created by removing sediment to a set elevation and remedial capping. Appendix I, Figure I-14 shows a schematic of the proposed shallow sheltered bay and submerged shoal.
5.3.3 Other Habitat/Recreational Elements While not explicitly shown, remedies could provide the substrate or starting point for other ecological or recreational goals and do not preclude implementation of the majority of habitat elements described in the conceptual habitat plans for the lower St. Louis River (SLR-CAC, 2002) and Spirit Lake (LimnoTech, 2012).
5.4 Assembled Alternatives for Screening-Level Evaluation The following twelve alternatives were assembled based on discussions with, and input from the MPCA, GLNPO, resource managers, and tribal representatives. Figures 5-1 through 5-12 illustrate these alternatives. The destinations for onsite management of removed sediments are shown by arrows on the figures.
The remedial footprints addressed by the alternatives are illustrated on Figure 5-1. The Former Operations areas exceeding RAOs are outlined in green and the estuary areas exceeding sediment PRGs are shown in
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purple. Approximate removal volumes, capping areas, CDF heights and change in open water areas for each alternative is summarized in Table 5-1.
5.4.1 Alternative 1 – Natural Recovery Alternative 1 involves no action beyond restricting public access to the site. The alternative is included as a baseline for the evaluation of alternatives. Figure 5-1 shows the areas evaluated in this FS and to which this alternative would apply. No material would be removed or actively capped and there would be no change to the area of open water.
5.4.2 Alternative 2 – Remedial Capping Alternative 2 includes placement of a 2-foot thick soil cap over the Former Operations sediment/soil impact areas and placement of varying thicknesses of capping material in the estuary to provide a remedial cap over the areas identified as “Remedial Cap” on Figure 5-2. No material would be removed as part of Alternative 2. Due to placement of the remedial cap, the shoreline shifts to the east in shallow capping areas, identified as “New Shoreline” on Figure 5-2, resulting in a loss of open water. Storm water flow within the Unnamed Creek would be channelized and diverted to the Wire Mill Intake Area of the estuary to preserve the integrity of the capped areas. Limited storm water ponding capacity would be retained upstream of the weir at OU-I to mitigate peak flows; however, ponding capacity would be reduced due to cap placement without removal of impacted sediment.
The conceptual layout illustrates the general effects of capping near shore; however, details of new shoreline shaping and grading to match existing bathymetry are not conceptualized on the preliminary illustration. Additional details regarding matching capped areas to site bathymetry and shoreline shape would need to be developed.
5.4.3 Alternative 3 – Delta/Estuary CDF (Confined Disposal Facility) Alternative 3 includes excavation of impacted Former Operations area soil and sediments and placement of a 2-foot thick soil cap over OU-I, the CDA and the OU-M area west of the railroad tracks. Alternative 3 also includes removal of estuary sediments that exceed PRGs from near the shoreline in the southern portion of the Wire Mill Delta and the northern portion of the Unnamed Creek Delta (identified as “Remove” on Figure 5-3). Removal of sediments to a set elevation and remedial capping is proposed on the northeast edge of the confined disposal facility (CDF) (identified as “Remove to Set Elevation and Cap” on Figure 5-3). This alternative also includes placement of a remedial cap or ENR thin cover over portions of the estuary area. Storm water flow upstream of the weir would be compatible with current conditions and would include similar ponding capacity of peak flows. Storm water would be diverted to the Wire Mill Intake Area downstream of the weir to deflect flow away from a CDF placed within the OU-M delta. Figure 5-3 shows a map view of this alternative.
Removed/Excavated Material Management – Materials will be consolidated in a single CDF that extends over the OU-M delta into the estuary. The CDF berm will be 4 feet high.
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Change in Open Water – Open water is created as a result of excavating sediment from the OU-P and OU-Q areas; however, because a portion of the CDF is within the estuary there is a net loss of open water (Table 5-1).
5.4.4 Alternative 4 – CDF on OU-M Delta (within Shoreline) Alternative 4 includes excavation of impacted Former Operations Area soil and sediment and placement of a 2-foot thick soil cap over OU-I, the CDA and the OU-M area west of the railroad tracks. Alternative 4 also includes removal of estuary sediments that exceed PRGs from near the shoreline in the southern portion of the Wire Mill Delta and the northern portion of the Unnamed Creek Delta (identified as “Remove” on Figure 5-4). Removal of sediments to a set elevation and remedial capping is proposed in the Unnamed Creek Delta (identified as “Remove to Set Elevation and Cap” on Figure 5-4). The alternative also includes placement of a remedial cap or ENR thin cover over portions of the estuary area. Storm water flow upstream of the weir would be similar to current conditions and would include similar ponding capacity of peak flows because OU-I sediment would be removed to a set elevation and then covered with a remedial cap. Storm water management features would be included as discussed in Section 5.2.10. Storm water would be diverted to the Wire Mill Intake Area downstream of the weir to deflect flow away from a CDF placed within the OU-M delta. Figure 5-4 illustrates the alternative.
Removed/Excavated Material Management – Materials will be consolidated in a single CDF within the OU-M delta area. The CDF berm will be 8 feet high. Contrasting with Alternative 3, the proposed CDF foot-print would be contained entirely within OU-M delta.
Change in Open Water – Open water is created as a result of excavating sediment from areas near the shoreline, resulting in a net gain of open water.
5.4.5 Alternative 5 – CDF with Open Water Bay Shown on Figure 5-5, Alternative 5 includes excavation of impacted Former Operations Area soil and sediments and placement of a 2-foot thick soil cap over OU-I, the CDA and the OU-M area west of the railroad tracks. Additionally, restored estuary will be created where impacted material excavated from the northern and western sides of the OU-M delta creates an open water bay similar in depth to the off shore portion of the existing Unnamed Creek delta area.
Alternative 5 also includes removal of sediments that exceed PRGs from near the shoreline in the southern portion of the Wire Mill Delta and the northern portion of the Unnamed Creek Delta (identified as “Remove” on Figure 5-5). Additional sediment will be dredged from the northern portion of the Unnamed Creek estuary delta (the shelf area), where sediments will be removed to a target elevation and a remedial cap will be placed (identified as “Remove to Set Elevation and Cap” on Figure 5-5). The alternative also includes placement of a remedial cap or ENR thin cover over portions of the estuary area. A submerged shoal would be constructed at the mouth of the bay to serve as an energy dissipation barrier between the bay and the greater estuary and as a remedial cap, if the shoal is constructed over remaining sediment exceeding PRGs.
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Storm water flow upstream of the weir would be similar to current conditions and would include similar ponding capacity of peak flows. Downstream of the weir, storm water flow would be directed to the shallow open water bay created in the OU-M delta. This alternative provides additional storm water ponding in the OU-M area west of the railroad tracks/OU-L area of Unnamed Creek.
Removed/Excavated Material Management – Materials will be consolidated in two locations under Alternative 5. The primary consolidation area will be a CDF that is located in the southern portion of the OU-M delta and extends into the estuary. A secondary consolidation area, comprised of impacted sediment removed from the Area Between OU-I and OU-J and OU-I, will be placed behind OU-J over the T-10 and T-11 SAs. CDF berm heights range from 9 to 25 feet.
Change in Open Water – A portion of the OU-M CDF extends into the estuary; however, an overall net gain of open water is created as a result of excavating sediment from areas near the shoreline (at OU-P and OU-Q) and from creating the open water bay.
5.4.6 Alternative 6 – Shallow Sheltered Bay with CDF Alternative 6 includes excavation of impacted soil and sediments and placement of a 2-foot thick soil cap over OU-I, the CDA and the OU-M west of the railroad tracks, as shown on Figure 5-6. Restored estuary will be created where impacted material excavated from the northern portion of the OU-M delta and placed along the spit-of land, creating a shallow (3 to 5 feet water depth) sheltered bay.
Alternative 6 also includes removal of sediments that exceed PRGs from near the shoreline in the southern portion of the Wire Mill Delta and the northern portion of the Unnamed Creek Delta (identified as “Remove” on Figure 5-6). Additional sediment will be dredged from the northern portion of the Unnamed Creek estuary delta (the shelf area), where sediments will be removed to a target elevation and a remedial cap will be placed (identified as “Remove to Set Elevation and Cap” on Figure 5-6). As noted above, the shallow sheltered bay will have an average water depth of 3 to 5 feet. The alternative also includes placement of a remedial cap or ENR thin cover over portions of the estuary area. A submerged shoal would be constructed at the mouth of the shallow sheltered bay to serve as an energy dissipation barrier between the bay and the greater estuary and as a remedial cap.
Storm water flow upstream of the weir would be similar to current conditions and would include similar ponding capacity of peak flows. Downstream of the weir, storm water flow would be directed to the shallow sheltered bay created in the OU-M delta.
Removed/Excavated Material Management – Materials will be primarily consolidated in a linear CDF of varying-height that is located in the southern portion of the OU-M delta and extends both westward and into the estuary. The CDF topographic contours would be sloped such that areas bordering open water would be low and increase in height to the south (near the spit of land) and west (on the west side of OU-M). Only estuary sediments will be managed within the footprint of the low CDF that is east of the railroad tracks. A secondary consolidation area, comprised of impacted sediment removed from the Area Between OU-I and OU-J and OU-I, will be placed behind OU-J over the T-10 and T-11 SAs. CDF berm heights range from 6 to 25 feet.
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Change in Open Water – A portion of the OU-M CDF extends into the estuary; however, an overall net gain of open water is created as a result of excavating sediment from areas near the shoreline (at OU-P and OU-Q) and from creating the shallow sheltered bay.
5.4.7 Alternative 7 – Shallow Sheltered Bay and Delta Cap Area with Upland CDFs
Alternative 7 is illustrated on Figure 5-7. Alternative 7 includes excavation of impacted soil and sediment and placement of a 2-foot thick soil cap over the CDA. Additionally, restored estuary will be created where impacted material will be excavated from the northern portion of the OU-M delta, creating a shallow sheltered bay (average water depth of 3 to 5 feet).
Alternative 7 also includes removal of sediments that exceed PRGs from near the shoreline in the southern portion of the Wire Mill Delta and the northern portion of the Unnamed Creek Delta (identified as “Remove” on Figure 5-7). Additional sediment will be dredged from the northern portion of the Unnamed Creek estuary delta (the shelf area), where sediments will be removed to a target elevation and a remedial cap will be placed (identified as “Remove to Set Elevation and Cap” on Figure 5-7). As noted above, the shallow sheltered bay will have an average water depth of 3 to 5 feet. The alternative also includes placement of a remedial cap or ENR thin cover over a portion of the estuary area. A submerged shoal would be constructed at the mouth of the bay to serve as an energy dissipation barrier between the bay and the greater estuary and as a remedial cap.
Storm water flow under Alternative 7 is constrained by consolidation of impacted material within the Unnamed Creek corridor. Flow would be channelized along the entire Unnamed Creek segment until it discharges to the shallow sheltered bay created in the OU-M delta. The capacity to pond storm water during major precipitation and run-off events would largely be eliminated as the existing weir would be removed for consolidation of impacted materials.
Removed/Excavated Material Management – Materials will be consolidated under Alternative 7 in three CDFs located entirely within the Former Operations portion of the Site west of the existing railroad grade. The OU-J CDF, comprised of material excavated from OU-P, OU-Q and storm water channel construction, would be placed behind OU-J (covering the T-10 and T-11 SAs) in a manner similar to previously discussed alternatives and would extend eastward to OU-I. Additional material removed from OU-P, OU-Q and storm water channel construction would be placed in a second CDF over OU-I and extend from the OU-J CDF east to the current location of the Site access road. The OU-L/western OU-M CDF would serve as a consolidation area for material excavated from Unnamed Pond, OU-M delta, as well as material dredged from the estuary. Because of the large volume of sediment in the OU-L/OU-M CDF, containment berms will be constructed with steeper side slopes and geotechnically reinforced to effectively confine the sediments. Both the OU-I and OU-L/OU-M CDFs will be bounded on the north/northwest by the Unnamed Creek storm water conveyance channel and will extend to the top of a natural bench located to the southeast. The CDF berm height will range from 13 to 25 feet.
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Change in Open Water – An overall net gain of open water is created as a result of excavating sediment from areas near the shoreline (at OU-P and OU-Q) and from creating the shallow sheltered bay.
5.4.8 Alternative 8 – Shallow Sheltered Bay with Delta Sediment CDF and Former Operations Area CDFs
Figure 5-8 illustrates this alternative. Alternative 8 includes excavation of impacted soils and sediment and placement of a 2-foot thick soil cap over OU-I and the CDA. Additionally, restored estuary will be created where impacted material will be excavated from the northern portion of the OU-M delta, creating a shallow sheltered bay (average water depth of 3 to 5 feet).
Alternative 8 also includes removal of sediments that exceed PRGs from near the shoreline in the southern portion of the Wire Mill Delta and the northern portion of the Unnamed Creek Delta (identified as “Remove” on Figure 5-8). Additional sediment will be dredged from the northern portion of the Unnamed Creek estuary delta (the shelf area), where sediments will be removed to a target elevation and a remedial cap will be placed (identified as “Remove to Set Elevation and Cap” on Figure 5-8). As noted above, the shallow sheltered bay will have an average water depth of 3 to 5 feet. In this alternative those sediments removed to the target elevation from the northern OU-M delta would be consolidated in a single source, estuary sediment CDF in the southern portion of the OU-M Delta and extending into the estuary. Only sediments removed from the adjoining estuary area will be consolidated in this location. The alternative also includes placement of a remedial cap or ENR thin cover over portions of the estuary area.
Storm water flow upstream of the weir would be similar to current conditions and would include similar ponding capacity of peak flows. Downstream of the weir, storm water flow would be directed to the shallow sheltered bay created in the OU-M delta.
Removed/Excavated Material Management – The majority of the materials will be consolidated in the CDF located in the OU-L/OU-M area. The OU-L/OUM CDF would maintain the same foot-print as described above in Alternative 7 but consolidate less material due to the absence of OU-M delta sediment; resulting in minimized view-shed impacts and less complicated construction. A smaller amount of excavated soil/sediment will be consolidated in the OU-J area in a manner previously described in this report section. As described above, a third estuary only CDF would be constructed within OU-M delta extending along the spit of land. The CDF berm heights will range from 6 to 25 feet. A submerged shoal would be constructed at the mouth of the bay to serve as an energy dissipation barrier between the bay and the greater estuary and as a remedial cap.
Change in Open Water – An overall net gain of open water is created as a result of excavating sediment from areas near the shoreline (at OU-P and OU-Q) and from creating the shallow sheltered bay.
5.4.9 Alternative 9 – Delta Cover and Upland CDFs Alternative 9 is illustrated on Figure 5-9. Alternative 9 includes excavation of impacted soil and sediment and placement of a 2-foot thick soil cover over the CDA, OU-I and western OU-M. Alternative 9 also includes removal of sediments that exceed PRGs from near the shoreline in the southern portion of the Wire Mill Delta and the northern portion of the Unnamed Creek Delta (identified as “Remove” on
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Figure 5-9). The alternative also includes removal of non-native sediments to a set elevation near the OU-M delta (identified as “Remove to Set Elevation and Cap” on Figure 5-9). Placement of a remedial cap or ENR thin cover over an expanded area is included as part of the alternative.
Storm water flow upstream of the weir would be similar to current conditions and would include similar ponding capacity of peak flows. Flow would be channelized downstream of the weir along the northern margins of a CDF placed within the OU-L/OU-M area until it discharges to a drainage feature along the toe of the OU-M delta bluff line.
Removed/Excavated Material Management – Materials will primarily be consolidated in an upland CDF that is located in the OU-L/OU-M area. A secondary consolidation area, comprised of impacted sediment removed from the Area Between OU-I and OU-J and OU-I, will be placed behind OU-J over the T-10 and T-11 SAs. CDF berm heights will range from 14 to 25 feet.
Change in Open Water – Open water is created as a result of excavating sediment from areas near the shoreline at OU-P and OU-Q.
5.4.10 Alternative 10 – Targeted Removal with Coke Plant Area CDF Alternative 10 is illustrated on Figure 5-10. Alternative 10 involves removal of impacted soils and sediment from the T-10/T-11 SA, the tar between OU-I and OU-J area, OU-I, OU-L, western OU-M, OU-M delta (to a target elevation), OU-P and OU-Q and the Unnamed Pond SA followed by placement of a remedial cap over the OU-I and the OU-M delta. The CDA will receive a remedial cap similar to that described in Alternative 9. The removed sediments would be placed into an upland CDF as described in Section 5.2.9. The consolidation location was selected based on proximity and accessibility to receive the removed materials and in a location of former foundations with the objective of minimizing loss of upland development area. However, development area would be lost on the upland property.
Alternative 10 also includes removal of sediments that exceed PRGs from near the shoreline in the southern portion of the Wire Mill Delta and the northern portion of the Unnamed Creek Delta (identified as “Remove” on Figure 5-10). Placement of a remedial cap or ENR thin cover over portions of the estuary area is included as part of the alternative.
Removed/Excavated Material Management – All removed materials would be placed over the former coke battery area within a CDF. The CDF would compass 34 acres with a berm height of 26 feet. The upland CDF is shown conceptually as a rectilinear feature for FS evaluation purposes, but the shape of this feature could be softened to mimic similar slopes nearby- this would be evaluated and addressed during the design phase.
Change in Open Water – Open water is created as a result of excavating sediment from areas near the shoreline at OU-P, OU-Q, OU-M, and OU-L areas.
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5.4.11 Alternative 11 – Removal with Large Coke Plant Area CDF Alternative 11 is illustrated on Figure 5-11. Alternative 11 involves removal of all impacted soils and sediment encompassed by the feasibility study. Alternative 11 also includes removal of sediments that exceed PRGs throughout both the Wire Mill and Unnamed Creed Deltas (identified as “Remove” on Figure 5-11). No remedial cap is included as part of the alternative.
Removed/Excavated Material Management – All removed materials would be placed over the former coke battery within a CDF. The CDF would encompass 76 acres and will have a berm height of 26 feet. The upland CDF is shown conceptually as a rectilinear feature for FS evaluation purposes, but the shape of this feature could be softened to mimic similar slopes nearby- this would be evaluated and addressed during the design phase.
Change in Open Water – Open water is created as a result of excavating sediment from areas near the shoreline, denoted “New Open Water” on Figure 5-11.
5.4.12 Alternative 12 – Open Water Bay with Upland CDFs Figure 5-12 illustrates this alternative. Alternative 12 includes excavation of impacted soils and sediment and placement of a 2-foot thick soil cap over OU-I and the CDA. Additionally, restored estuary will be created where impacted material will be excavated from the OU-M delta, creating an open water bay (average water depth of 1 to 3 feet).
Alternative 12 also includes removal of sediments that exceed PRGs from near the shoreline in the southern portion of the Wire Mill Delta and the northern portion of the Unnamed Creek Delta (identified as “Remove” on Figure 5-12). Additional sediment will be dredged from the Unnamed Creek estuary delta (the shelf area), where sediments will be removed to a target elevation and a remedial cap will be placed (identified as “Remove to Set Elevation and Cap” on Figure 5-12). As noted above, the open water bay will have an average water depth of 1 to 3 feet. A submerged shoal would be constructed at the mouth of the bay to serve as an energy dissipation barrier between the bay and the greater estuary and as a remedial cap. In this alternative those sediments removed to the target elevation from the northern OU-M delta would be removed from the estuary and consolidated in one of several upland CDFs. The alternative also includes placement of a remedial cap or ENR thin cover over portions of the estuary area.
Storm water flow upstream of the weir would be similar to current conditions and would include similar ponding capacity of peak flows. Downstream of the weir, storm water flow would be directed to the shallow sheltered bay created in the OU-M delta.
Removed/Excavated Material Management – The majority of the materials will be consolidated in two locations – a CDF located in the OU-L/western OU-M area and an upland CDF located south of the OU-P/OU-Q area in an area referred to as the Borrow Site. The OU-L/western OU-M CDF would maintain the same foot-print as in Alternative 7 and 8 but the available storage capacity would be maximized, resulting in potential view-shed impacts. Except for the small amount of material consolidated in the OU-J area (as previously described in this report), all soil/sediment that does not fit into the CDF at the OU-
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L/OU-M area would be consolidated in the Borrow Site upland CDF. The upland CDFs are shown conceptually as a rectilinear features for FS evaluation purposes, but the shapes of these features could be softened to mimic similar slopes nearby- this would be evaluated and addressed during the design phase.
Change in Open Water – There is an overall net gain of open water as a result of excavating sediment from areas near the shoreline (at OU-P and OU-Q) and from creating the open water bay (OU-M Delta).
5.5 Screening-Level Evaluation of Alternatives This section discusses the screening-level evaluation of the eleven assembled alternatives described in Section 5.4. In performing this screening-level evaluation, the eleven alternatives were given a relative score with respect to three comparative screening categories and compared to one another.
The screening-level criteria used to evaluate the 11 alternatives include:
x Effectiveness at achieving remedial action objectives (RAOs)
x Implementability
x Relative cost
Table 5-2 presents the relative evaluation of the alternatives. The first two columns of the table list the eleven alternatives and provide a description of each. Figures 5-1 through 5-11 provide schematic maps showing the layout and key elements of each alternative.
The effectiveness with which an alternative would achieve the RAOs is ranked as high, with a score of 1, to low, with a score of 5. The numeric effectiveness scoring of 1 to 5 is described in the key provided at the bottom of Table 5-2. A similar scoring range for implementability uses the highest score of 1 and the lowest implementability score of 5. Relative costs are compared between the alternatives and a relative cost score is assigned with the lowest cost alternatives assigned 1 and the highest relative cost alternatives assigned scores of 5. Cost-ranking was based on engineering judgment, experience with similar Projects, and preliminary development of site-specific cost estimates, which were carried forward for use in detailed evaluation of retained alternatives as described in Section 5.7. The sum of the scores for the three relative evaluation categories for each alternative is provided as the screening level score included in Table 5-2 and are used to rank the alternatives. Additional factors for consideration are also noted and used to identify the alternatives that were selected for detailed evaluation.
To aid in screening the alternatives, the table cells are shaded with colors according to the key at the bottom of Table 5-2. The best performing alternatives are shaded light gray. The poorest performing alternatives are shaded red. In this scheme of scoring and color-coding, individual criteria can be visualized for their contributions to the lowest overall scoring alternatives.
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In summary, the alternatives fell into three groups, ranging from most favorable to least favorable:
x Alternatives 4, 5, 6 and 8 had the lowest screening level score (7)
x Alternatives 2, 3, 7, 9, and 12 had a moderate screening level score (ranging from 9 to 10)
x Alternatives 10 and 11 had the greatest screening level scores (12 and 13, respectively)
Additional factors for consideration were also included in Table 5-2 and were used in conjunction with the screening level score to identify alternatives that would be evaluated in detail. These additional factors included whether habitat goals are met by one approach versus another, whether aquatic habitat would be lost, and how stormwater was managed.
5.5.1 Alternatives Retained for Detailed Evaluation Based on multiple meetings, discussions and reviews by the Project Partners, consultation with resource managers, and the screening evaluation included in Table 5-2; the following proposed focused list of alternatives was identified for detailed evaluation in the FS.
x Alternative 4 – CDF on OU-M Delta (within Shoreline)
x Alternative 6 – Shallow Sheltered Bay with Low CDF
x Alternative 7 – Shallow Sheltered Bay and Delta Cap Area with Upland CDFs
x Alternative 8 – Shallow Sheltered Bay with Delta Sediment CDF and Upland CDFs
x Alternative 12 – Open Water Bay with Upland CDFs
Alternative 4 is retained as it represents an efficient approach to managing impacted estuary sediments by consolidating impacted material on top of impacted sediments on OU-M Delta. Alternative 4 is a modification of, and scores better than, Alternative 3 which was determined to have more wetland permitting requirements along with a net loss of open water habitat. Alternative 5 was one of the lowest scoring alternatives, but was not retained for detailed evaluation because it was similar to Alternative 6 and had less water depth in the open water bay (average of 1 to 2 ft water depths) than the shallow sheltered bay (average of 3 to 5 ft water depths) in Alternative 6.
Alternative 7 was not one of the lowest scoring alternatives, but was retained to provide a comparison with Alternative 8. Both of these alternatives provide habitat enhancement elements in the Unnamed Creek Delta area, but differ in how storm water is managed and location and type of CDFs constructed. Alternative 8 manages some estuary sediments in a CDF beside the spit of land which allows upland CDFs to be placed in a manner that provides for stormwater retention in the Unnamed Creek drainage way (a ponding area in the OU-I area). In contrast, Alternative 7 manages all Site sediments in 3 upland CDFs with taller berms than Alternative 8, but also restricts storm water flow, thereby increasing water velocities of stormwater and doesn’t provide ponding from storms. These aspects were determined by the Project
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partners to be important comparison points and therefore Alternative 7 was retained for detailed evaluation with three selected low-scoring alternatives (4, 6, and 8).
Alternative 12 was also not one of the lowest scoring alternatives, but was retained as an option that did not involve consolidation of any impacted material east of the railroad tracks, based on feedback from Project partners. Alternative 12 manages all Site sediments in three upland CDFs, two of which would have taller berms than Alternative 8 and one which would require longer haul distances for removed sediments. Because the Project partners indicated that it was important to evaluate an alternative that managed material removed from the unnamed creek delta in locations west of the railroad tracks, Alternative 12 was retained for detailed evaluation along with the three selected low-scoring alternatives (4,6, and 8) and with Alternative 7 (retained for comparison with Alternative 8).
5.6 Detailed Evaluation of Retained Alternatives The detailed evaluation of retained alternatives involves evaluating each of the five alternatives with respect to the USEPA’s National Contingency Plan (NCP) remedy evaluation criteria (40 CFR §300.430). The seven evaluation criteria are summarized in Table 5-3; two additional modifying criteria, State/Tribal and Community Acceptance, are evaluated after the public comment period. In addition, the detailed evaluation considered the USEPA Principles for Managing Contaminated Sediment Risks at Hazardous Waste Sites (EPA, 2002). These eleven principles are summarized in Table 5-4. Other factors that were also considered include the USEPA Contaminated Sediment Remediation Guidance for Hazardous Waste Sites (EPA, 2005) and the Minnesota Environmental Response and Liability Act (MERLA, Minn. Stat. § 115B). Tables 5-5 through 5-9 provide detailed evaluations with respect to the Seven Criteria for each retained alternative. Table 5-10summarizes the results of the detailed evaluation and compares each of the five alternatives to one another. In Table 5-10 a new scoring of 1 to 5, is applied for each criterion according to the key at the bottom of the page. A low score value is most desirable.
The estimated costs of the alternatives retained for detailed evaluation are summarized in Table 5-11. These costs were developed in detail using unit quantities for the remedial alternatives described in Section 5.5.1 and unit costs that were developed based on bid tabs for similar recent projects, R. S. Means, supplier quotes, and professional judgment. Estimated operation and maintenance costs were developed for the five detailed alternatives to be considered with the estimated remediation implementation cost for each and are listed in Table 5-11. It should be noted that the level of design detail is low at the FS stage of evaluation. Therefore, both estimated implementation costs as well as post-construction operation and maintenance costs are based on a set of assumptions and information that are limited in nature due to the conceptual level of detail. The cost information is developed for the purposes of general comparison and evaluation of feasibility and it is normal for the cost estimate ranges used for evaluating feasibility, to vary from the actual costs. The objective of developing general ranges of operation and maintenance cost for each of the detailed alternatives is to evaluate whether any of the alternatives may have a significantly higher operation and maintenance level of effort needed once the remedy is constructed. Specific details and requirements of operation and maintenance will be developed during the design phase and may also be subject to modification or updating once the construction is completed and the remedy has been
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monitored for a period of time. For all these reasons, the operation and monitoring costs provided in Table 5-11 are given as ranges.
The total scores for each of the five alternatives indicate that Alternative 7, with a score of 20, has the highest score (least favorable) primarily due to high scores for short-term effectiveness, implementability and cost. Alternative 12 has the second highest score of 17 (less favorable) mainly due to implementability and cost- this alternative requires three upland CDFs, one of which is located a significant distance from the removal area and requires a significant excavation to construct along with a liner system. Alternative 6 has the third highest (less favorable) score of 15 due to implementability and cost. Alternative 4 is the lowest cost of the four alternatives, but its score of 13 is the same as Alternative 8, which has significant advantages in habitat creation. Alternative 8 is indicated to be the best-performing alternative based on the criteria, principles, and Project goals (Table 5-10).
5.7 Recommended Alternative Based on the screening evaluation and the detailed analysis, Alternative 8-Shallow Sheltered Bay with Delta Sediment CDF and Upland CDFs compares most favorably to the remedy evaluation criteria, principles and additional habitat considerations. It scored in the best performing group in the screening evaluation (Table 5-2) and has the best ranking in the detailed evaluation (Table 5-10).
Alternative 8 embodies numerous key elements of the remediation goals and habitat goals for the Former Operations and estuary areas of the site. It is reflective of important priorities identified by stakeholder input such as the creation of two shallow sheltered bay habitat areas; features which are currently absent in Spirit Lake. The need for shallow sheltered bay habitat is discussed in the Lower St. Louis River Habitat Plan (SLR-CAC, 2002) and Lower St. Louis River Habitat Plan Strategies Implementation Planning Worksheet: Project 2.7: Sheltered Bays/Shallow Wetlands- Spirit Lake (LimnoTech, 2012). In addition, the recommended alternative includes important stormwater retention elements in the Unnamed creek drainage way. This Alternative incorporates a mixture of remedial technologies and was developed out of an iterative, risk-based decision-making process that sought, and included input from various groups throughout the FS development process.
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6.0 Recommendations and Path Forward This FS has evaluated Site conditions and developed a series of Conceptual Site Models to provide a detailed understanding of the nature, extent, and magnitude of COIs across the Former Operations and Estuary portions of the Site. Using the process outlined in this FS, potential Project alternatives have been identified, screened, and evaluated in detail to identify a preferred alternative. Input was received at multiple stages as outlined in the preceding sections of the FS. Most recently the U.S. EPA has entered into formal tribal consultations under Section 106 of the National Historic Preservation Act (NHPA). As noted in Sections 1.0 and 5.0 an additional alternative was identified as a result of those consultations and that alternative was evaluated with four other alternatives, the results of that evaluation are set forth in Section 5.0.
This section of the FS includes a discussion of the recommended Project alternative and outlines the path forward for implementation of a Project in the Former Operations and the Estuary areas.
6.1 Recommended Project Alternative Using the FS process, which was initiated with technology screening and the assembly of potential Project alternatives, a total of twelve Project alternatives were identified for screening. After the initial screening, which included input from both the MPCA and GLNPO, five alternatives were selected for detailed evaluation. During the draft FS review, tribal consultation was begun and the number 12 alternative was developed. As a result of the screening evaluation, Alternative 12 was carried forward through the detailed evaluation described in Section 5.6.
Alternative 8-Shallow Sheltered Bay with Delta Sediment CDF and Upland CDFs was identified in Section 5.7 as the best overall Project alternative because it compares most favorably with the threshold criteria while providing the most consistent balance of considerations for the balancing criteria, providing betterment of the St. Louis River AOC through key habitat benefits such as the creation of two shallow sheltered bay areas, creation of more locations with water depth transitions from shallow to deeper water and shoal areas that can provide future sites for emergent vegetation establishment, key habitat goals are met for the estuary site. Alternative 8 provides these features in accordance with the conceptual goals of the AOC habitat objectives set forth in the Lower St. Louis River Habitat Plan (SLR-CAC, 2002) and the Lower St. Louis River Habitat Plan Strategies Implementation Planning Worksheet: Project 2.7: Sheltered Bays/Shallow Wetlands- Spirit Lake (LimnoTech, 2012).
Alternative 8 reflects a balance of factors with respect to how it manages sediment in separate areas-Former Operations area sediments and some estuary sediments are consolidated in upland CDFs within the UC ravine where the CDF facilities have lower visual impact and can take some advantage of the valley side to help contain the material. A trade-off is required, however, due to space limitations and stormwater flow needs within the upper UC; which means that some estuary sediments, removed to create a shallow sheltered bay in the OU-M Delta area, are consolidated along with the remainder of the in-place OU-M Delta material in a low CDF constructed against the northern side of the Spit of Land. This will result in a broadened peninsula beside what will be a longer and deeper embayment on the north.
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The full thickness of sediments exceeding the PRGs will be removed from the WM Delta shore area and OU-P and -Q. This results in partially recreating the topography of the embayment that existed in this location prior to the Duluth Works site development. This results in an increase in open water and creation of a second shallow sheltered bay habitat area. Alternative 8 increases open water area by 20 acres, which is another important goal of the AOC delisting effort for the lower St. Louis River (SLR-CAC, 2002 and LimnoTech, 2012).
Comparison of the LimnoTech (2012) Spirit Lake Conceptual (Habitat) Restoration Plan with the preferred alternative, identified that although the spit of land will remain with a broad low CDF on its northern side, the majority of the project area will be available for implementing the conceptual plan for habitat improvements in Spirit Lake. Overall the preferred remedy is consistent with the conservation goals set forth in the Restoration Concept Plan. All four of the general habitat types identified in the plan would not be precluded by Alternative 8. Open water – shallow, mid- and deep-water areas either already exist or would not be precluded over most areas of Spirit Lake. Shallow and deep marsh area could be expanded and would not be precluded by Alternative 8. Saturated islands could be developed as broadly outlined in the Restoration Concept Plan. A technical memorandum was submitted to the MPCA and EPA in March 2015 (Barr, 2015). Hydrodynamic conditions should be taken into consideration when planning any habitat restoration work that might affect water flows and sediment transport.
The sustainability of Alternative 8 is also consistent with the overall Vision for this Project (Section 3). This alternative is consistent with the USEPA’s National Contingency Plan (NCP) remedy evaluation criteria (40 CFR §300.430), the Minnesota Environmental Response and Liability Act (MERLA, Minn. Stat. § 115B), the USEPA Principles for Managing Contaminated Sediment Risks at Hazardous Waste Sites (EPA, 2002), and the USEPA Contaminated Sediment Remediation Guidance for Hazardous Waste Sites (EPA, 2005).
The 11 risk management principles outlined in the EPA guidance (EPA, 2002) are summarized below with a brief discussion of how each principle has been applied throughout the RI/FS process and how Recommended Alternative 8 is fully consistent with the Sediment Management Principles.
Principle 1 – Control Sources Early
The sources of COIs identified in site sediments were primarily wastewater discharges from facilities formerly located on the site and urban runoff/stormwater that flows across the site. The majority of the site operations ceased in 1979, with most of the buildings and other structures razed by the late 1980s, thereby eliminating the wastewater discharges. Several control measures including in situ stabilization, excavation, dredging, capping and covering were implemented in the late 1980s and 1990s to limit the amount of COI-impacted material in the stormwater drainage system that discharges to Spirit Lake. Urban runoff and atmospheric fallout and the river’s wash load continue, but are not likely sources to impact site sediments at concentrations above the PRGs for the Site or require additional remedial or restoration activities. Alternative 8 includes restoration elements that control stormwater conveyance on the site to limit the potential for COI-impacted sediment from causing recontamination of site sediments.
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Principle 2 – Involve the Community Early and Often
The Morgan Park, West Duluth and greater Duluth community have been involved throughout the RI/FS process, including numerous community meetings to solicit community input and discuss remediation and restoration project goals and progress. Future land use has been the subject of significant discussion with the City of Duluth, the Port Authority and other interested stakeholders during the RI/FS process and is one of the elements considered during remedial alternative evaluation. In addition to remediation elements, Alternative 8 also includes restoration elements that address discussions from the community and stakeholder meetings.
Principle 3 – Coordinate with States, Local Governments, Tribes and Natural Resource Trustees
The RI/FS process has involved a significant coordination among U. S. Steel, the federal government (EPA Region 5 and GLNPO), state government (MPCA and MDNR), local government (City of Duluth and Port Authority), tribes (Fond du Lac and 1854 Treaty Authority) and the natural resource trustees (USF&W, NOAA, and St. Louis River Alliance). The MPCA and EPA (Region 5 and GLNPO) were involved in extensive discussions with U. S. Steel to develop the remediation alternatives evaluated in this FS over several years, including, most recently, a presentation of the draft FS conclusions to a group of St. Louis River estuary resource managers. Alternative 8 includes remediation and restoration elements suggested by stakeholders during the many discussion.
Principle 4 – Develop and Refine a Conceptual Site Model that Considers Sediment Stability
The CSMs developed for the site and presented in Section 2 of this FS summarize the interrelationships of soil, surface and groundwater, sediment and ecological and human receptors. The CSMs are iterative and the results of the site investigations completed at the site to date, including sediment coring, geotechnical drilling and hydrodynamic/sediment transport modeling have been incorporated to assess the temporal, physical and chemical forces that affect the sediment stability at the site. Alternative 8 addresses the interrelationships evaluated in the CSMs and evaluates and factors the sediment stability in Spirit Lake and potential effects on ecological and human receptors.
Principle 5 – Use an Iterative Approach in a Risk-Based Framework
As described in Principle 4, above, iterative CSMs have been used to compile site data, interrelationships, observations and model results to evaluate potential risks presented by sediment impacted by COIs at the site. The CSMs have been updated as new information became available (and will continue to be used during the permitting and design phase) and used to evaluate the potential risks to ecological and human receptors represented by different remedial alternatives. Alternative 8 successfully incorporates remediation components that reduce the potential risks to receptors, including potential recontamination of site sediments.
Principle 6 – Carefully Evaluate the Assumptions and Uncertainties Associated with Site Characterization Data and Site Models
Iterative use of the CSMs to evaluate remedial options has included identification of assumptions and potential uncertainties in site data, observations and model results. Subsequent investigations,
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observations and modeling have been completed to verify or refute assumptions and refine and inform uncertainties. The investigation, observations and models used during the RI/FS process have been completed in accordance with work plans reviewed by the MPCA and EPA (Region 5 and GLNPO). Hydrodynamic modeling completed for Spirit Lake involved consultation and recommendations from Deltares, the developer of the Delft3D model used for the site and one of the leading coastal process research institutes in the world, during model set up, data collection, and results review. The major 2012 storm and flood provided corroboration of model results predicting areas of sediment erosion and deposition and confirmed the very positive information that substantial deposition of clean sediment occurred in the Estuary as a result of the storm. Site characterization and modeling results have been used to develop appropriate remediation alternatives included in Alternative 8.
Principle 7 – Select Site-Specific, Project Specific, and Sediment-Specific Risk Management Approaches that will Achieve Risk based Goals
The FS includes a detailed evaluation of 12 remedial alternatives developed in consultation with the MPCA and EPA (Region 5 and GLNPO) that incorporate different combinations of the numerous remediation and restoration elements considered. No presumptive remedy was identified prior to the evaluation included in Section 5. Recommended Alternative 8 includes an excellent balance of remediation and restoration elements that manage potential risks by addressing a broad set of environmental, natural resources, property use and other stakeholder interests and goals.
Principle 8 – Ensure that Sediment Cleanup Levels are Clearly Tied to Risk Management Goals
As discussed in the context of Principle 5, an iterative approach has been used to evaluate risk, and the uncertainty of those risks has been addressed via discussion of RI/FS results and potential remediation and restoration alternatives with stakeholders. Attainment of the sediment cleanup levels (designated as PRGs at this site) through the appropriate application of dredging and capping technologies is expected to control ecological and human health risks from the COIs at the site. Site-specific sediment PRGs, identified by the MPCA and presented in Section 2, have been used to determine areas of the site requiring remediation, appropriate remediation alternatives to control and limit potential receptor pathways, and to evaluate the effectiveness of the potential remediation alternatives in achieving protection of human health and the environment. Alternative 8 is expected to meet appropriate risk-management goals, including attainment of the site’s sediment PRGs.
Principle 9 – Maximize the Effectiveness of Institutional Controls and Recognize their Limitations
Institutional controls may be used to enhance and support active remediation measures such as dredging, containment and capping, which will be the primary means of limiting exposure to COIs at the site. Institutional controls that may be used at the site are summarized in Section 5.2.1.
Principle 10 – Design Remedies to Minimize Short-term Risks while Achieving Long-term Protection
Evaluation of short-term risks and long-term protection for each of the remediation alternatives is included in Section 5, which demonstrates that the short-term risks during remedy implementation are minimal and that the recommended remedy will be protective on a long-term basis.
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Principle 11 – Monitor During and After Sediment Remediation to Assess and Document Remedy Effectiveness
Construction quality assurance and environmental monitoring will be completed during site remediation and restoration activities to ensure compliance with project RAOs, PRGs and other goals. The details of the monitoring program, including but not limited to, media, sample location and frequency, laboratory analysis methods, data quality objectives, compliance standards, and approval or rejection criteria, will be detailed in the quality assurance project plan (QAPP), construction quality assurance plan (CQAP), and sampling and analysis plan (SAP) that will be completed during the permitting and design phase. A long-term monitoring plan will be implemented after completion of the remediation activities to monitor remedy effectiveness.
Added benefits to the recommended alternative are the improvements that could occur to the shoreline and shallow water areas of the Site once the remedial work is completed. Opportunities will exist for incorporating further habitat enhancements along the reconstructed shoreline. Previously prohibited shoreline and shallow water uses such as recreational access could be improved. The post-remedy configuration of shore features will be planned in consultation with the current land owners and neighboring stakeholders during Project design.
In addition, upland areas (Former Operations area) of the site are maintained for future redevelopment opportunities.
6.2 Path Forward U. S. Steel, GLNPO and MPCA are following an aggressive path forward for the remaining pre-implementation activities described in Section 6.2.1 in order to meet the goal of beginning construction of the preferred alternative during 2016.
6.2.1 Pre-Implementation Activities To meet this desired Project implementation schedule, several tasks will need to occur in parallel. Below is a summary of the primary pre-implementation tasks that need to occur prior to Project implementation.
x FS review
x Public comment on, and final approval of, the proposed remedy
x Secure Legacy Act funding for the Project implementation phase
x EAW preparation, public comment, and expeditious EIS decision (Appendix G)
x Design development
o Habitat elements included in design
o Coordination with resource managers
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x Collect supplemental sediment data to refine PRG extent and determine remedy element boundaries to support design, including areas with adjacent remedy elements – in progress
x Conduct supplemental geotechnical sampling and testing to support design for Alternative 8 – in progress
x Negotiate and implement property access agreements and agreements regarding reconstruction of areas disturbed by the remedy construction, including replacement or new infrastructure
x Permitting coordination, application preparation, and agency review (Appendix G)
x Preparation of contractor bid documents, review contractor bids and select contractor
The MPCA will assist with the EAW and the permit review process to help meet the Project schedule.
6.2.2 Project Implementation The recommended alternative is anticipated to require two full construction seasons to complete. Specific Project implementation schedules will be included as part of the design and will be determined based on input from the selected response action contractor.
Implementation of the recommended alternative, or any of the other alternatives retained for detailed analysis, may require full-time (24 hours per day/7 days per week) project operations at some areas of the Site. The remedial design and associated documents, including the construction quality assurance plan, response action contractor implementation plan, Site-specific health and safety plan, and applicable permits or other regulatory requirements will determine the methods and frequency of monitoring to ensure compliance with applicable standards and guidelines, including noise, air emission quality, surface water quality and turbidity.
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7.0 References AECOM, 2014. Preliminary Geotechnical Assessment, OU-M Delta Area, Former U. S. Steel Duluth Works.
Technical Memorandum to John Prusiecki (USS) - Prepared November, 2014 by AECOM (formerly URS) for U. S. Steel. Forwarded to Minnesota Pollution Control Agency and US Environmental Protection Agency Great Lakes National Program Office, July 2015. Note - this document was originally included as Appendix I in the Draft Feasibility Study Report (November, 2014).
ASCE, 2007. In Situ Capping of Contaminated Sediments with Reactive Materials. J.T. Olsata. Proceedings of Ports 2007: 30 Years of Sharing Ideas 1977-2007. American Society of Civil Engineers (ASCE). March 25-28, 2007.
Barr, 1986. Remedial Investigation Final Report: USS Duluth Works Site. Prepared for USS, a division of USX Corporation. Report Volume One and Appendix Volume Two.
Barr, 1990. A Review of Alternative and Innovative Treatment Technologies for Polynuclear Aromatic Hydrocarbon (PAH) Contaminated Soil, USX Duluth Works Site. Prepared for USS June 1990.
Barr, 2012. Final Feasibility Study Work Plan. Spirit Lake Sediment Site - Former U. S. Steel Duluth Works Saint Louis River, Duluth, Minnesota. Prepared for U. S. Steel, August 2012.
Barr, 2013b. Habitat Characterization Report – 2012. Spirit Lake Sediment Site - Former U. S. Steel Duluth Works Saint Louis River, Duluth, Minnesota. Prepared for U. S. Steel and U.S. EPA Great Lakes National Program Office, May 2013.
Barr, 2013a. Sediment Remedial Investigation Report. Great Lakes Legacy Act Project - Spirit Lake Sediment Site - Former U. S. Steel Duluth Works Saint Louis River, Duluth, Minnesota. Prepared for U. S. Steel and U.S. EPA Great Lakes National Program Office, March 2013.
Barr, 2014a. U. S. Steel Spirit Lake Sediment Site Technical Memorandum – Potential Influence of Plants, Invertebrates, Vertebrates and Physical Processes on Sediment. February 12, 2014.
Barr, 2014b. Revised Information for Human Health Risk Analysis for U. S. Steel. Technical Memorandum (draft) to Minnesota Pollution Control Agency, Ms. Susan Johnson, Ms. Bonnie Brooks. Prepared by Barr Engineering for U. S. Steel, July 14, 2014. Submitted in response to MPCA-requested information dated June 6, 2014. Includes: Package 1 – July 14, 2014 Draft Tech memo with 3 figures. Package 2 – Email transmittal confirming data package provided electronically to MPCA via file transfer site dated July 31, 2014. Package 3 – hard copy of data package, tables, figures and UCL Statistics summaries, dated July 31, 2014. Receipt of materials confirmed by email correspondence from Ms. Susan Johnson and Ms. Bonnie Brooks (MPCA).
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Barr, 2014c. Geotechnical Evaluation of Estuary Site Alternatives, Former Duluth Works and Spirit Lake Sediment Site. Prepared for U. S. Steel Corporation, November, 2014 by Barr Engineering Company. Forwarded to Minnesota Pollution Control Agency and US Environmental Protection Agency Great Lakes National Program Office, July 2015.Note - this document was originally included as Appendix I in the Draft Feasibility Study Report (November, 2014)
Barr, 2014d. Draft Feasibility Study: Former Duluth Works and Spirit Lake Sediment Site (two volumes). Prepared for Great Lakes Legacy Act Partnership between United States Steel Corporation, and United States, Environmental Protection Agency, Great Lakes National Program Office; in consultation with Minnesota Pollution Control Agency. Prepared by Barr Engineering Company, EA Engineering, Science, and Technology, Inc., URS Corporation, November 2014.
Barr, 2015. Technical Memorandum- Comparison of Spirit Lake Conceptual Restoration Plan to Preferred Remedy in (Draft 2014) FS. March 4, 2015. To John Prusiecki (U. S. Steel), Scott Cienowski (US EPA Great Lakes National Program Office), Copies to Mark Rupnow (U. S. Steel), Susan Johnson (MPCA). From Jamie Bankston, Jeff Lee, Don Richard, Eric Dott (Barr).
Duluth Archeology Center, 2013, Documentation of Information for National Registry of Historic Places Regarding Spirit Island in the St. Louis River, St. Louis County, Minnesota, Duluth Archeology Center Report Number 13-11, Report to Fond du Lac Band of Lake Superior Chippewa, May, 2013
EA, 2013. Technical Memorandum for Comparison of Surficial Porewater and Sediment Concentrations of Polycyclic Aromatic Hydrocarbons and Metals – Spirit Lake Sediment Site – Fall 2012 Supplemental Sampling Effort – St. Louis River Area of Concern, Duluth, Minnesota. Prepared for U.S. EPA Region 5, December 2013.
EA, 2014. Spirit Lake Contaminated Sediment Treatability Study – St. Louis River Area of Concern, Duluth, Minnesota. Prepared for U.S. EPA Region 5, April 2014.
EPA, 1994. ARCS Remediation Guidance Document. EPA 905-B94-003. Chicago, Ill.: Great Lakes National Program Office.
EPA, 2002. Principles for Managing Contaminated Sediment Risks at Hazardous Waste Sites. U.S. EPA, Office of Emergency and Remedial Response, Washington D.C., OSWER Directive 928 5.6-08, February 12, 2002.
EPA, 2005. Contaminated Sediment Remediation Guidance for Hazardous Waste Sites. U.S. EPA, Office of Emergency and Remedial Response, Washington D.C., OSWER Directive 9355.0-85, December 2005.
EPA, 2010. Superfund Green Remediation Strategy. U.S. EPA, Office of Emergency and Remedial Response and Office of Superfund Remediation and Technology Innovation. September 2010.
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Fitzpatrick, F.A., Peppler, M.C., DePhilip, M.M. and Lee, K.E., 2006. Geomorphic Characteristics and Classification of Duluth-Area Streams, Minnesota, USGS Scientific Investigations Report 2006-5029, 2006.
Geraghty and Miller, 1996. Response Action Plan – Operable Unit – J, U. S. Steel Duluth Works Site, Duluth, Minnesota.
ITRC, 2014. Contaminated Sediments Remediation: Remedy Selection for Contaminated Sediments (CS-2). Washington D.C.: Interstate Technology & Regulatory Council, Contaminated Sediments Team. http://www.itrcweb.org/contseds_remedy-selection.
LimnoTech, 2012. Lower St. Louis River Habitat Plan Strategies Implementation Planning Worksheet, Project 2.7: Sheltered Bays/Shallow Wetlands – Spirit Lake, Conceptual Restoration Plan, prepared for the Minnesota Pollution Control Agency with funding from GLRI, October 19, 2012.
LimnoTech, 2013. St Louis River Area of Concern Implementation Framework: Roadmap to Delisting (Remedial Action Plan Update), prepared for the St. Louis River Alliance with funding from the GLRI Grant No. GL00E00556, July 15, 2013.
Lindholm, G.F., Ericson, D.W., Broussard, W.L. and Hult, M.F., 1979. Water Resources of the St. Louis River Watershed, Northeastern Minnesota. Hydrologic Investigations Atlas HA-586, prepared for the United States Geological Survey. 3 plates.
SLR-CAC, 1992. St. Louis River Response Action Plan- Stage-1. Prepared by St Louis River Citizens Action Committee, April 1992.
SLR-CAC, 2002. Lower St. Louis River Habitat Plan. Prepared by SLR CACSt. Louis River Citizens Action Committee with funding from U.S. EPA Grant X995385010, May, 2002.
MPCA, 1989. Record of Decision. Record of Decision for the U. S. Steel Site. (Available at: http://www.pca.state.mn.us/index.php/view-document.html?gid=3275), February 1989.
MPCA, 2007. Guidance for the Use and Application of Sediment Quality Targets for the Protection of Sediment-Dwelling Organisms in Minnesota. MPCA Document Number: tdr-gl-04, February 2007.
MPCA, 2014a. E-mail from Susan Johnson to Mark Rupnow and John Prusiecki, RE: Upland Soils PRGs, May 23, 2014.
MPCA, 2014b. Letter from Susan Johnson to Mark Rupnow and John Prusiecki, RE: Interim Remedial Action Objectives, Preliminary Remedial Goals, and Bioactive Zone (BAZ) for the U. S. Steel Duluth Works Site, March 5, 2014.
UEC, 1993. Report of Phase II Environmental Site Assessment, Former Steel Works, Duluth Works Site, Duluth, Minnesota, December 1993.
73
USACE, 2008. The Four Rs of Environmental Dredging: Resuspension, Release, Residual, and Risk. Dredging Operations and Environmental Research Program. ERDC/EL TR-08-4.
URS, 2013. Remedial Investigation Addendum, Former U. S. Steel Duluth Works Site. October, 2013.
74
Tables
Table 3-1 TERRESTRIAL CRITERIA BY ANTICIPATED FUTURE LAND USE Former U. S. Steel Duluth Works - Spirit Lake Sediment Site
Saint Louis River Duluth, Minnesota
Element/Compound Recreational SRV* Industrial SRV* Arsenic 11 20 Copper 100 9,000 Lead 300 700 Mercury 1.2 1.5 Naphthalene 24 28 BaP Equivalents 2 3
* SRVs are currently under review
P:\Duluth\23 MN\69\23691125 St Louis River Duluth Works Sediment\WorkFiles\P_Feasibility Study\FS-Report\2015 Revised FS Tables\Table 3-1 - Terr Crit by Anticipated Future Land Use.xlsx
7/15/20151:07 PM
Tabl
e 3-
3
EXTE
NT
OF
IMPA
CTS
Fo
rmer
U. S
. Ste
el D
ulut
h W
orks
- Sp
irit L
ake
Sedi
men
t Site
Sa
int L
ouis
Rive
r Du
luth
, Min
neso
ta
Area
Co
mpa
rison
Crit
eria
Ho
rizon
tal E
xten
t Ve
rtic
al E
xten
t
Tar I
mpa
cted
Soi
l (Ar
eas T
-10
and
T-11
)
MPC
A Ti
er 2
ISRV
s (ex
ceed
ance
s not
ed fo
r ars
enic
, le
ad a
nd se
lect
PAH
s) a
nd e
colo
gica
l SRV
s (e
xcee
danc
es in
clud
ed m
etal
s and
PAH
s).
A te
st p
it in
vest
igat
ion
iden
tifie
d a
late
ral z
one
of
impa
ct o
f app
roxi
mat
ely
0.5
acre
s at T
-10
and
appr
oxim
atel
y 2,
000
squa
re fe
et a
t T-1
1.
The
full
thin
knes
s of n
on-n
ativ
e m
ater
ial a
t T-1
0 in
cos
ider
ed im
pact
ed a
bove
PRG
s. T
est p
its in
th
e vi
cini
ty o
f T-1
1 id
entif
ied
tar w
ithin
the
uppe
rmos
t tw
o fe
et.
Non
-nat
ive
Mat
eria
l in
the
Sett
ling
Basin
(OU
-I)
Leve
l I a
nd L
evel
II S
QTs
. Le
vel I
SQ
T ex
ceed
ance
s w
ere
note
d fo
r bot
h m
etal
s and
PAH
con
stitu
ents
. Le
vel I
I exc
eeda
nces
wer
e lim
ited
to se
lect
met
als.
The
horiz
onta
l ext
ent o
f im
pact
ed u
plan
d se
dim
ent
at O
U-I
(app
roxi
mat
ely
6.78
acr
es) i
s con
stra
ined
by
topo
grap
hic
feat
ures
ass
ocia
ted
with
the
hist
oric
cok
e pl
ant s
ettli
ng b
asin
and
adj
acen
t Ous
.
The
full
thic
knes
s of n
on-n
ativ
e se
dim
ent w
ithin
O
U-I
is co
nsid
ered
impa
cted
abo
ve P
RGs.
The
ba
se o
f the
upl
and
sedi
men
t ext
ends
to
appr
oxim
atel
y 60
6 fe
et a
msl.
Tar a
nd T
ar-Im
pact
ed S
oil i
n th
e Co
ke P
lant
Set
tling
Bas
in (T
ar
betw
een
I & J)
Leve
l I a
nd L
evel
II S
QTs
. Le
vel I
and
Lev
el II
SQ
T ex
ceed
ance
s wer
e no
ted
for b
oth
met
als a
nd P
AHs.
The
1.2
acre
are
a of
impa
cted
upl
and
sedi
men
t is
cons
trai
ned
by to
pogr
aphi
c fe
atur
es a
ssoc
iate
d w
ith th
e hi
stor
ic c
oke
plan
t set
tling
bas
in a
nd
adja
cent
OU
s.
The
full
thic
knes
s of n
on-n
ativ
e se
dim
ent w
ithin
th
e ar
ea b
etw
een
OU
-I an
d O
U J
is co
nsid
ered
im
pact
ed a
bove
PRG
s.
Stre
am C
hann
el (O
U-L
) Le
vel I
and
Lev
el II
SQ
Ts.
Leve
l I a
nd L
evel
II S
QT
exce
edan
ces w
ere
note
d fo
r bot
h m
etal
s and
PAH
s.
The
horiz
onta
l ext
ent o
f OU
-L, a
ppro
xim
atel
y 3.
2 ac
res,
is im
pact
ed u
plan
d se
dim
ent
The
full
thic
knes
s of n
on-n
ativ
e se
dim
ent w
ithin
O
U-L
is c
onsid
ered
impa
cted
abo
ve P
RGs.
The
ba
se o
f the
upl
and
sedi
men
t ext
ends
to
appr
oxim
atel
y 59
8 fe
et A
MSL
.
Delta
and
Str
eam
Cha
nnel
(OU
-M)
Leve
l I a
nd L
evel
II S
QTs
. Le
vel I
and
Lev
el II
SQ
T ex
ceed
ance
s wer
e no
ted
for b
oth
met
als a
nd P
AHs.
The
horiz
onta
l ext
ent o
f im
pact
ed u
plan
d se
dim
ent
is ap
prox
imat
ely
46 a
cres
, con
stra
ined
by
topo
grap
hic
feat
ures
.
The
full
thic
knes
s of n
on-n
ativ
e se
dim
ent w
ithin
O
U-M
is c
onsid
ered
impa
cted
abo
ve P
RGs.
Wire
Mill
Pon
d (O
U-P
)
MPC
A Ti
er 2
ISRV
s (ex
ceed
ance
s not
ed fo
r lea
d),
ecol
ogic
al S
RVs (
exce
edan
ces i
nclu
ded
met
als a
nd
PAHs
) and
Lev
el I
and
Leve
l II S
QTs
(exc
eeda
nces
wer
e no
ted
for b
oth
met
als a
nd P
AHs)
.
The
horiz
onta
l ext
ent o
f im
pact
ed u
plan
d se
dim
ent
is co
nstr
aine
d by
topo
grap
hic
feat
ures
ass
ocia
ted
with
the
Wire
Mill
sett
ling
basin
(app
roxi
mat
ely
1.1
acre
s).
The
full
thic
knes
s of n
on-n
ativ
e se
dim
ent w
ithin
O
U-P
is c
onsid
ered
impa
cted
abo
ve P
RGs.
The
ba
se o
f the
upl
and
sedi
men
t ext
ends
to
appr
oxim
atel
y 58
7 fe
et A
MSL
.
Non
-nat
ive
Mat
eria
l and
Dre
dge
Spoi
ls in
Wire
Mill
Set
tling
Bas
in
(OU
-Q)
MPC
A Ti
er 2
ISRV
s (ex
ceed
ance
s not
ed fo
r ars
enic
, le
ad a
nd b
enzo
(a) p
yren
e eq
uiva
lent
s).
Furt
her
eval
uatio
n of
OU
-Q d
redg
e sp
oils
was
per
form
ed in
or
der t
o de
velo
p di
spos
al o
ptio
ns fo
r ele
vate
d le
vels
of le
ad in
soil.
Soi
l was
foun
d to
exc
eed
the
toxi
city
ch
arac
teris
tic fo
r lea
d.
The
horiz
onta
l ext
ent o
f sed
imen
t im
pact
s at O
U Q
en
com
pass
es a
n ar
ea o
f app
roxi
mat
ely
6.4
acre
s.
The
late
ral e
xten
t of a
n ar
ea e
xhib
iting
ele
vate
d le
ad in
dre
dge
spoi
ls on
the
perip
hery
of O
U-Q
has
no
t bee
n de
fined
.
The
full
thic
knes
s of n
on-n
ativ
e se
dim
ent w
ithin
th
e w
etla
nd p
ortio
n of
OU
-Q is
con
sider
ed
impa
cted
abo
ve P
RGs.
Dre
dge
spoi
ls al
ong
the
perip
hery
of O
U-Q
ext
end
up to
8 fe
et b
elow
gr
ade.
Conc
rete
Disp
osal
Are
a (C
DA)
MPC
A Ti
er 2
ISRV
s (ex
ceed
ance
s not
ed fo
r ars
enic
and
se
lect
PAH
s) a
nd e
colo
gica
l SRV
s (ex
ceed
ance
s in
clud
ed m
etal
s, P
AHs,
VO
Cs a
nd P
CBs)
. Al
kalin
e so
ils
also
are
pre
sent
.
The
horiz
onta
l ext
ent o
f che
mic
al im
pact
s and
non
-na
tive
fill e
ncom
pass
es 1
3 ac
res,
as
dete
rmin
ed b
y te
s t p
it an
d so
il bo
ring
inve
stig
atio
ns.
The
vert
ical
ext
ent o
f che
mic
al im
pact
s and
non
-na
tive
fill w
ere
obse
rved
to a
max
imum
dep
th o
f 32
f eet
bel
ow g
rade
.
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uth
Wor
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tudy
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Exte
nt o
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51:1
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Tabl
e 3-
3
EXTE
NT
OF
IMPA
CTS
Fo
rmer
U. S
. Ste
el D
ulut
h W
orks
- Sp
irit L
ake
Sedi
men
t Site
Sa
int L
ouis
Rive
r Du
luth
, Min
neso
ta
Area
Co
mpa
rison
Crit
eria
Ho
rizon
tal E
xten
t Ve
rtic
al E
xten
t
Unn
amed
Pon
d Le
vel I
and
Lev
el II
SQ
Ts.
Leve
l I a
nd L
evel
II S
QT
exce
edan
ces w
ere
note
d fo
r bot
h m
etal
s and
PAH
s.
The
horiz
onta
l ext
ent o
f im
pact
ed u
plan
d se
dim
ent
is as
sum
ed to
ext
end
acro
ss th
e 0.
2 ac
re fo
ot-p
rint
of th
e U
nnam
ed P
ond.
Impa
cted
upl
and
sedi
men
ts w
ere
enco
unte
red
vert
ical
ly w
ithin
the
four
feet
dee
p in
vest
igat
ion
zone
. N
ativ
e m
ater
ial w
as n
ot e
ncou
nter
ed.
Wire
Mill
Del
ta
Leve
l I a
nd L
evel
II S
QTs
. Le
vel I
and
Lev
el II
SQ
T ex
ceed
ance
s wer
e no
ted
for b
oth
met
als a
nd P
AHs.
The
horiz
onta
l ext
ent o
f im
pact
ed se
dim
ent i
s as
sum
ed to
ext
end
acro
ss a
ppro
xim
atel
y 90
acr
es
of th
e W
ire M
ill D
elta
.
The
impa
cted
sedi
men
ts in
the
Wire
Mill
Del
ta
rang
es fr
om u
p to
4 ft
thic
k ne
ar sh
ore
to le
ss
than
0.5
ft th
ick
offs
hore
.
Unn
amed
Cre
ek D
elta
Le
vel I
and
Lev
el II
SQ
Ts.
Leve
l I a
nd L
evel
II S
QT
exce
edan
ces w
ere
note
d fo
r bot
h m
etal
s and
PAH
s.
The
horiz
onta
l ext
ent o
f im
pact
ed se
dim
ent i
s as
sum
ed to
ext
end
acro
ss a
ppro
xim
atel
y 90
acr
es
of th
e U
nnam
ed C
reek
Del
ta.
The
impa
cted
sedi
men
ts in
the
Unn
amed
Cre
ek
Delta
rang
es fr
om m
ore
than
10
ft th
ick
near
sh
orel
ine
to le
ss th
an 0
.5 ft
offs
hore
.
P:\D
ulut
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ouis
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uth
Wor
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s\P_
Feas
ibili
ty S
tudy
\FS-
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015
Revi
sed
FS T
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3-3
Exte
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Table 3-5 FORMER OPERATIONS AREA STORMWATER CONVEYANCE GOALS
Former U. S. Steel Duluth Works - Spirit Lake Sediment Site Saint Louis River
Duluth, Minnesota
GOAL OBJECTIVE CRITERIA Stormwater Conveyance
Contain flowing stormwater within the structures (including ponds), box culverts, channels, and embankments of the stormwater conveyance system to limit erosion and routine maintenance requirements
Base flow and frequent events (10-year, 24-hour design storm) Caps: 10-year, 24-hour design storm
Flood Management Avoid increasing the flood level downstream of the project and avoid adverse on-site impacts from flooding
100-year, 24-hour design storm
Containment Design conveyances and caps to protect sediments that are capped in place from susceptibility to further transport; limit potential for erosion and scour by specifying materials, and designing conveyances and caps, to remain stable under a range of anticipated velocities and flow characteristics
Base flow 10-year, 24-hour design storm 100-year, 24-hour design storm
p:\duluth\23 mn\69\23691125 st louis river duluth works sediment\workfiles\p_feasibility study\fs-report\2015 revised fs tables\table 3-5 -former operations area stormwater conveyance goals.docx
Table 3-7 POTENTIAL RECEPTORS DRIVING HABITAT ZONE THICKNESS Former U. S. Steel Duluth Works - Spirit Lake Sediment Site
Saint Louis River Duluth, Minnesota
Habitat Zone Thickness
(cm) Applicable Areas Potential Receptors
Backshore / Foreshore 120 x x x
Shoreline/beach areas Sediment flats Open water/transition
x
x
Deep rooted herbaceous and/or woody plants Deep burrowing mammals
Emergent Aquatic Vegetation
100
x
x
Wetlands and areas of emergent aquatic vegetation Potential for emergent aquatic vegetation
x x
Emergent aquatic vegetation Deep burrowing amphibians, reptiles, or crustaceans
Submerged Aquatic Vegetation and Deep
Water 50
x
x x
No potential to transition to wetland Deep water Armored areas or areas with root barriers
x x
Benthic organisms Submerged aquatic vegetation
Reference: MPCA Letter dated March 2014 (MPCA, 2014b)
p:\duluth\23 mn\69\23691125 st louis river duluth works sediment\workfiles\p_feasibility study\fs-report\2015 revised fs tables\table 3-7_pot_rec_hz_thick.docx
a nn a t n t
Des
crip
tion
iona
l con
trols
in th
e fo
rm o
f an
nmen
tal r
estri
ctiv
e co
vena
nt o
r on
s of
futu
re p
erm
its m
ay b
e us
ed to
t e
xpos
ure
and
cont
act w
ith im
pact
ed
sedi
men
t by
rest
rictin
g la
nd u
ses
or
ance
s to
the
mat
eria
l.
ves
impa
cted
sed
imen
t in
plac
e an
d on
ong
oing
, nat
ural
ly o
ccur
ring
ses
to is
olat
e, d
estro
y, o
r red
uce
ur
e or
toxi
city
of i
mpa
cted
sed
imen
t.
dds
amen
dmen
ts to
the
soil
or s
edim
ent
eler
ate
phys
ical
isol
atio
n pr
oces
s a
nd
tes
re-e
stab
lishm
ent o
f ben
thic
or p
lant
. M
ay in
clud
e a
gran
ular
or c
arbo
n t c
over
(ove
r sed
imen
ts) o
r bio
logi
cal
ants
(to
soil)
.
ng p
rovi
des
a ph
ysic
al b
arrie
r and
ca
l iso
la io
n fro
m C
OIs
. C
aps
may
be
ucte
d fro
m c
lean
sed
imen
t, sa
nd, g
rave
l, til
es, l
iner
s, re
activ
e or
abs
orpt
ive
al a
nd m
ay c
onsi
st o
f mul
tiple
laye
rs (5
). ar
sed
imen
t cap
s ca
n pr
ovid
e er
osio
n io
n an
d lim
it bi
otur
batio
n (1
).
ent i
s lif
ted
to th
e su
rface
usi
ng a
ni
cal e
xcav
ator
or c
rane
and
pla
ced
on
e fo
r tra
nspo
rt. R
emov
ed s
edim
ent h
as
ar m
oist
ure
cont
ent a
s th
e in
situ
al
, req
uirin
g de
wat
erin
g pr
ior t
o di
spos
al
esid
ual c
over
is ty
pica
lly n
eede
d to
e
rem
aini
ng i
mpa
cts.
Site
Estu
ary
App
licab
ility
to S
ite
May
incl
ude
fish
cons
umpt
ion
advi
sorie
s, c
omm
erci
al fi
shin
g ba
ns,
wat
erw
ay u
se re
stric
tions
, an
d de
ed re
stric
tions
.(1)
Ran
king
R
etai
ned
f C
onsi
dera
t
Yes
Yes
Effe
ctiv
enes
s
H
ighl
y ef
fect
ive
in s
ome
estu
ary
loca
tions
, whe
n co
mbi
ned
with
oth
er
tech
nolo
gies
and
inst
itutio
nal c
ontro
ls.
Effe
ctiv
e at
mee
ting
rem
edia
tion
goal
s w
hen
com
bine
d w
ith o
ther
rem
edie
s.
Im
plem
enta
bilit
y
Im
plem
enta
ble.
Pla
cem
ent r
equi
res
Site
acc
ess,
sta
ndar
d se
dim
ent
rem
edia
tion
equi
pmen
t and
re
susp
ensi
on c
ontro
ls.
Eas
ily im
plem
ente
d w
ith li
ttle
disr
uptio
n to
he
site
at a
ny s
tage
of
the
rem
edia
l pro
cess
. z z
Hig
hly
impl
emen
tabl
e. N
o co
nstru
ctio
n, in
frast
ruct
ure,
or h
eavy
eq
uipm
ent i
s re
quire
d.
Rela
tive
Cost
M
inim
al b
ut th
ere
are
long
term
cos
ts
asso
ciat
ed w
ith in
i iat
ing
and
mai
ntai
ning
inst
itutio
nal c
ontro
ls.
$$
Gre
ater
cos
t tha
n N
R d
ue to
thin
co
ver o
r am
endm
ent p
lace
men
t, bu
t lo
w c
ompa
red
to s
edim
ent r
emov
al
and
capp
ing.
$
The
mai
n co
st o
f NR
is a
ssoc
iate
d w
ith m
onito
ring,
if re
quire
d.
$
Upl
and
Estu
ary
May
incl
ude
rest
rictio
ns o
n ex
cava
tion
or ty
pes
of
deve
lopm
ent.
Alre
ady
occu
rring
at t
he s
ite in
so
me
area
s th
roug
h de
posi
ion
of
new
sed
imen
t lay
ers.
Upl
and
Estu
ary
NR
is o
ccur
ring
in s
ome
upla
nd
area
s, th
ough
rate
is s
low
.
May
enh
ance
NR
that
is a
lread
y oc
curri
ng in
som
e ar
eas.
M
argi
nally
effe
ctiv
e du
e to
thic
knes
s of
im
pact
s.
W
ould
acc
eler
ate
the
NR
pro
cess
, re
duci
ng ti
me
to m
eet S
MG
s.
No
Yes
Upl
and
Estu
ary
May
enh
ance
NR
in s
urfic
ial s
oils
.
Cap
thic
knes
s de
pend
s on
bi
oact
ive
zone
(BA
Z) th
ickn
ess
requ
irem
ents
, whi
ch v
ary
by
habi
tat,
subs
trate
and
wat
er
dept
h.
A c
ap m
ay a
lter h
ydro
logi
c an
d ha
bita
t con
ditio
ns in
the
estu
ary.
M
argi
nally
effe
ctiv
e du
e to
thic
knes
s of
im
pact
s.
zH
ighl
y ef
fect
ive
and
prov
en m
etho
d.
Site
CO
Is h
ave
low
sol
ubili
ty a
nd
mob
ility
, so
capp
ing
wou
ld b
e an
ef
fect
ive
cont
ainm
ent m
etho
d.
Hyd
rody
nam
ic m
odel
ing
sugg
ests
that
po
tent
ial s
cour
ing
by w
ave
actio
n is
no
t a s
igni
fican
t con
cern
.
Sho
rt te
rm m
ovem
ent o
f CO
Is in
po
rew
ater
is p
ossi
ble
durin
g co
nsol
idat
ion.
Te
chni
cally
cha
lleng
ing
in a
reas
of
deep
impa
cts.
D
redg
ing
may
be
requ
ired
in s
hallo
w
area
s to
acc
omm
odat
e ca
p th
ickn
ess.
Mul
tiple
laye
red
caps
may
requ
ire
spec
ializ
ed e
quip
men
t. A
dditi
onal
st
udy
is n
eede
d if
reac
tive
or
abso
rptiv
e m
ater
ials
are
use
d.
Mai
nten
ance
is m
anag
eabl
e gi
ven
the
stab
le h
ydro
dyna
mic
con
di io
ns.
$$
Cos
tly to
add
ress
dee
p im
pact
s w
ith
EN
R.
$$$
Mai
n ca
pita
l cos
ts in
clud
e eq
uipm
ent
mob
iliza
tion,
equ
ipm
ent o
pera
tion,
re
sidu
al c
over
mat
eria
ls, a
nd
cons
truc
ion
and
oper
atio
n of
a
cont
ainm
ent a
rea
for d
redg
ed
mat
eria
l.
$$$
Hig
her c
osts
than
mec
hani
cal
dred
ging
due
to th
e ne
ed fo
r m
echa
nica
l equ
ipm
ent t
o re
mov
e de
bris
, and
he
addi
tiona
l tre
atm
ent
and
disp
osal
cos
ts d
ue to
gre
ater
w
ater
con
tent
of t
he s
lurri
ed s
edim
ent.
Cos
ts a
re g
ener
ally
less
than
se
dim
ent r
emov
al, a
nd d
epen
d on
ca
p th
ickn
ess,
mat
eria
l, la
tera
l ext
ent
and
surfa
ce w
ater
eng
inee
ring
fact
ors.
Mat
eria
l cos
ts fo
r a s
ynth
etic
cap
are
ge
nera
lly h
ighe
r tha
n a
gran
ular
cap
.
$$$
No
Yes
Upl
and
Estu
ary
Estu
ary
Cap
ping
wou
ld c
ontro
l dire
ct
expo
sure
to im
pact
ed m
ater
ial
and
prev
ent e
rosi
on.
Mec
hani
cal m
etho
ds a
re re
quire
d to
rem
ove
debr
is in
he
Wire
Mill
se
dim
ents
and
the
cem
ente
d no
n-na
tive
sedi
men
ts in
the
Unn
amed
C
reek
Del
ta.
Res
uspe
nsio
n co
ntro
ls e
xpec
ted
to b
e ne
eded
.
Hyd
raul
ic m
etho
ds a
re n
ot
suita
ble
to re
mov
e de
bris
in th
e W
ire M
ill D
elta
or c
emen
ted
non-
nativ
e se
dim
ents
in th
e U
nnam
ed
Cre
ek D
elta
.
zH
ighl
y ef
fect
ive
and
prov
en m
etho
d.
zH
ighl
y ef
fect
ive
prov
en m
etho
d fo
r re
med
iatin
g im
pact
ed s
edim
ent.
Con
trolli
ng re
susp
ensi
on a
nd li
miti
ng
rede
posi
ion
and
trans
port
of im
pact
ed
sedi
men
t is
need
ed to
ach
ieve
sho
rt an
d lo
ng te
rm S
MG
s.
P
rove
n m
e ho
d fo
r rem
edia
ting
impa
cted
sed
imen
t, bu
t not
effe
ctiv
e at
re
mov
ing
debr
is o
r har
dene
d se
dim
ents
. Mec
hani
cal m
etho
ds w
ould
al
so b
e re
qiui
red.
zR
eadi
ly im
plem
ente
d in
upl
and
area
s.
R
equi
res
dred
ging
equ
ipm
ent a
nd
infra
stru
ctur
e fo
r tre
atm
ent,
trans
port,
an
d/or
dis
posa
l of d
redg
ed s
edim
ent.
Less
wat
er is
pro
duce
d co
mpa
red
to
hydr
aulic
dre
dgin
g, s
o le
ss s
pace
is
need
ed fo
r sed
imen
t/wat
er
man
agem
ent.
R
equi
res
hydr
aulic
dre
dgin
g eq
uipm
ent a
nd in
frast
ruct
ure
sim
ilar
to m
echa
nica
l dre
dgin
g.
Mor
e w
ater
trea
tmen
t and
spa
ce fo
r se
dim
ent m
anag
emen
t nee
ded
than
w
ith m
echa
nica
l dre
dgin
g du
e to
hig
h w
ater
con
tent
of s
lurry
.
Yes
Yes
Yes
ulic
dre
dgin
g ad
ds w
ater
to th
e se
dim
ent
mov
es it
by
pum
ping
it in
he
form
of a
ty
pica
lly th
roug
h a
pipe
line
to th
e er
ing
loca
tion
or fi
nal d
ispo
sal s
ite. H
igh
cont
ent o
f slu
rry re
quire
s si
gnifi
cant
er
ing.
Res
idua
l cov
er is
typi
cally
nee
ded
age
rem
aini
ng im
pact
s.
r
n
Des
crip
tion
is d
iver
ted
or d
rain
ed fr
om th
e at
ion
area
usi
ng a
con
tain
men
t bar
rier
s a
coffe
rdam
to a
llow
for e
xcav
atio
n of
di
men
t with
con
vent
iona
l equ
ipm
ent (
e.g.
oe
). Ty
pica
lly li
mite
d to
sha
llow
are
as.(1
)
rem
oved
with
con
vent
iona
l exc
avat
ion
men
t. C
omm
only
com
bine
d w
i h
g.
ved
soil
or s
edim
ent i
s tra
nspo
rted
to a
n di
spos
al lo
catio
n th
at w
ill a
ccep
t the
D
ewat
erin
g of
sed
imen
ts is
gen
eral
ly
d be
fore
tran
spor
t.
are
engi
neer
ed s
truct
ures
enc
lose
d by
an
d sp
ecifi
cally
des
igne
d to
con
tain
en
t. C
DFs
may
be
loca
ted
eith
er u
plan
d th
e w
ater
tabl
e), n
ear-s
hore
(par
tially
in
ter),
or c
ompl
etel
y in
he
wat
er (i
slan
d . ed
or e
xcav
ated
sed
imen
t is
disp
osed
a
natu
ral o
r exc
avat
ed d
epre
ssio
n he
re in
he
wat
er b
ody.
iliza
tion
treat
men
ts a
dd c
hem
ical
s or
ts
to re
duce
the
leac
habi
lity
of C
OIs
. ni
sms
incl
ude
solid
ifica
tion
sula
tion)
or s
tabi
lizat
ion
(che
mic
al o
r tiv
e re
actio
ns th
at c
onve
rt C
OIs
to le
ss
r mob
ile fo
rms)
. (2)
Site
Estu
ary
Upl
and
Estu
ary/
U
plan
d
Estu
ary/
U
plan
d
Estu
ary
Estu
ary
Upl
and
App
licab
ility
to S
ite
Wel
l sui
ted
for a
reas
in th
e U
nnam
ed C
reek
Del
ta w
ith
shal
low
wat
er d
epth
s an
d ge
omet
ry th
at a
llow
s fo
r co
nstru
ctio
n of
a c
onta
inm
ent
barri
er a
nd w
ater
div
ersi
on.
Eith
er c
ompl
ete
exca
vatio
n or
pa
rtial
exc
avat
ion
com
bine
d w
ith
capp
ing
may
mee
t RA
Os.
Tran
spor
tatio
n of
larg
e vo
lum
es o
f so
il an
d se
dim
ent w
ould
cre
ate
sign
ifica
nt tr
uck
traffi
c th
roug
h th
e su
rroun
ding
com
mun
ity fo
r a lo
ng
dura
tion.
Land
is a
vaila
ble
for a
CD
F.
Pla
cem
ent o
f a C
DF
near
sho
re in
th
e U
nnam
ed C
reek
Del
ta c
ould
ut
ilize
exi
stin
g ge
omet
ry fo
r co
ntai
nmen
t whi
le c
over
ing
impa
cted
sed
imen
ts in
this
are
a.
A s
uita
ble
loca
tion
to
acco
mm
odat
e al
l sed
imen
t vo
lum
es is
not
ava
ilabl
e du
e to
sh
allo
w w
ater
dep
ths.
The
wat
er
inta
ke h
ole
in th
e W
ire M
ill D
elta
an
d th
e dr
edge
d ch
anne
l in
the
Unn
amed
Cre
ek D
elta
cou
ld h
old
som
e vo
lum
e, b
ut th
ese
are
desi
rabl
e fis
h ha
bita
t are
as.
Impl
emen
tatio
n at
a s
edim
ent s
ite
is d
iffic
ult,
due
to w
ork
belo
w th
e w
ater
and
con
cern
s w
ith
tem
pora
ry p
H e
ffect
s an
d vo
latil
izat
ion
of C
OIs
.
Use
d su
cces
sful
ly a
t OU
-J, w
ith
som
e ch
alle
nges
; mod
ifica
ions
to
stor
m w
ater
sys
tem
wer
e re
quire
d.
Ran
king
Ef
fect
iven
ess
zR
emov
al o
f sed
imen
t in
dry
cond
ition
s al
low
s fo
r vis
ual i
nspe
ctio
n an
d is
ty
pica
lly m
ore
com
plet
e th
an w
ith
dred
ging
.
Ver
y lit
tle p
oten
ial f
or re
susp
ensi
on,
mob
iliza
tion
and
rede
posi
tion
of
impa
cted
sed
imen
t.
zH
ighl
y ef
fect
ive
and
prov
en m
etho
d.
zV
ery
effe
ctiv
e at
mee
ting
SM
Gs
and
RA
Os,
as
the
sedi
men
t wou
ld b
e re
mov
ed fr
om th
e si
te.
Som
e ris
k of
rele
ase
durin
g tra
nspo
rtatio
n.
zC
DFs
are
the
mos
t wid
ely
used
m
etho
d fo
r dis
posa
l of i
mpa
cted
se
dim
ents
and
hav
e de
mon
stra
ted
effe
ctiv
enes
s fo
r con
tain
men
t.
A
CA
D m
ay b
e ef
fect
ive
at c
onta
inin
g P
AH
s an
d m
etal
s du
e to
thei
r low
m
obili
ty a
nd s
olub
ility
. M
onito
ring
may
be
need
ed to
ver
ify
effe
ctiv
enes
s.
Mat
eria
ls u
sed
for c
onst
ruct
ion
need
to
prev
ent l
ater
al m
igra
tion.
Wav
e ef
fect
s at
the
CA
D s
ite w
ould
ne
ed to
be
eval
uate
d.
N
ot w
idel
y us
ed a
t sed
imen
t site
s.
Effe
ctiv
enes
s fo
r PA
Hs
dem
onst
rate
d at
som
e si
tes,
but
not
wid
ely
acce
pted
. P
rove
n ef
fect
ive
for m
etal
s in
soi
ls.
May
cre
ate
toxi
c co
nditi
ons
for b
enth
ic
orga
nism
s.
zTh
e ef
fect
iven
ess
for P
AH
s ha
s be
en
dem
onst
rate
d at
som
e si
tes,
but
is n
ot
wid
ely
acce
pted
. P
rove
n ef
fect
ive
met
hods
for m
etal
s in
soi
ls.
Impl
emen
tabi
lity
N
ot fe
asib
le fo
r all
estu
ary
area
s du
e to
he
larg
e re
mov
al a
reas
and
larg
e am
ount
of w
ater
to d
iver
t.
Site
pre
para
tion
com
plic
ated
and
le
ngth
y du
e to
wat
er m
anag
emen
t.
Impl
emen
tabl
e in
sha
llow
are
as
whe
re c
onta
inm
ent i
s fe
asib
le.
zR
eadi
ly im
plem
ente
d in
upl
and
area
s w
ith c
onve
ntio
nal e
arth
wor
k eq
uipm
ent.
Th
orou
gh d
ewat
erin
g is
requ
ired
to
mee
t lan
dfill
liqu
id re
stric
tions
.
The
site
is a
cces
sibl
e fo
r hau
l tru
cks,
bu
t tru
ck tr
affic
wou
ld c
ause
si
gnifi
cant
dis
rupt
ion,
dam
age
to
road
s an
d no
ise
conc
erns
. Ris
k of
off-
site
rele
ase
durin
g tra
nspo
rtatio
n.
C
DF
desi
gn re
quire
s de
taile
d kn
owle
dge
of th
e dr
edgi
ng p
lans
, se
dim
ent p
rope
rties
and
pre
dict
ed
efflu
ent q
ualit
y.
A C
DF
wou
ld b
e a
perm
anen
t st
ruct
ure
occu
pyin
g a
larg
e ar
ea.
Trea
tmen
t of t
he d
ewat
erin
g di
scha
rge
is li
kely
requ
ired.
A
n ex
is in
g de
pres
sion
larg
e en
ough
fo
r a C
AD
is n
ot a
vaila
ble.
Dre
dgin
g to
acc
omm
odat
e re
quire
d di
spos
al
volu
mes
wou
ld n
ot b
e co
st e
ffect
ive.
CA
D d
esig
n re
quire
s kn
owle
dge
of
sedi
men
t and
hyd
raul
ic c
ondi
tions
.
C
an b
e di
fficu
lt to
inje
ct a
nd
adeq
uate
ly m
ix re
agen
ts in
situ
.
The
solid
ified
mat
eria
l inc
reas
es in
vo
lum
e an
d co
uld
limit
futu
re s
ite
uses
, and
futu
re s
ite d
redg
ing.
P
ilot s
tudi
es a
nd e
valu
atio
n of
effe
cts
on s
urfa
ce w
ater
s re
quire
d.
The
solid
ified
mat
eria
l res
ults
in a
pe
rman
ent s
olid
stru
ctur
e be
low
gr
ound
.
Rela
tive
Cost
$$
$ C
osts
are
sim
ilar t
o m
echa
nica
l dr
edgi
ng c
osts
, with
the
adde
d co
st to
co
nstru
ct d
iver
sion
or c
onta
inm
ent
stru
ctur
es.
$$
Cos
ts d
epen
d hi
ghly
on
exca
vatio
n ex
tent
and
vol
ume.
Cos
t can
be
less
whe
n co
mbi
ned
with
ca
ppin
g to
min
imiz
e vo
lum
e of
ex
cava
ted
soil
and
back
fill.
$$$$
C
osts
for o
ffsite
dis
posa
l inc
lude
de
wat
erin
g, w
ater
trea
tmen
t, lo
adin
g an
d tra
nspo
rtatio
n co
sts
and
land
fill
disp
osal
fees
. Tr
ansp
orta
tion
cost
s de
pend
on
dist
ance
to th
e la
ndfil
l.
$$$
Cos
ts fo
r a C
DF
incl
ude
engi
neer
ing
and
desi
gn c
osts
, mat
eria
ls fo
r dik
es
and
susp
ende
d so
lids
cont
rol,
and
cons
truc
ion
equi
pmen
t and
labo
r.
$$$
Spe
cial
ized
equ
ipm
ent f
or a
CA
D m
ay
be re
quire
d, e
spec
ially
if th
e di
spos
al
site
is in
dee
p w
ater
.
Dre
dgin
g to
cre
ate
a C
AD
wou
ld a
dd
cost
.
$$$
Cos
ts fo
r sol
idifi
catio
n or
sta
biliz
atio
n af
fect
ed b
y th
e qu
antit
y an
d ty
pe o
f re
agen
ts a
dded
to th
e w
aste
and
the
need
for s
peci
aliz
ed e
quip
men
t for
m
ixin
g re
agen
ts w
ith s
edim
ent.
$$$
Lar
ge v
olum
es a
re c
ostly
to tr
eat.
Ret
aine
d f
Con
side
rat
Yes
Yes
No
- for
la
estu
ary
or O
U-
M a
reas
. H
ow
reta
ined
for l
oc
upla
nd s
oil i
m
area
on
hills
be
side
OU
-P
area
.
Yes
No
No
Yes
n, o
Des
crip
tion
ial d
egra
datio
n by
bac
teria
or f
ungi
is
ced
by a
ddin
g m
ater
ials
suc
h as
oxy
gen,
s
ulfa
te, h
ydro
gen,
nut
rient
s, o
r rg
anis
ms
to h
e se
dim
ent o
r soi
l.
cals
are
inje
cted
into
sed
imen
t to
act a
s da
nt/e
lect
ron
acce
ptor
to fa
cilit
ate
c de
com
posi
tion
of o
rgan
ic m
atte
r.
dditi
on o
f che
mic
al o
xidi
zers
to s
edim
ent
use
the
rapi
d an
d co
mpl
ete
chem
ical
c
ion
of m
any
toxi
c or
gani
c ch
emic
als
emed
iatio
n us
es p
lant
spe
cies
to
e, tr
ansf
er, s
tabi
lize,
and
des
troy
CO
Is in
d
sedi
men
t. G
ener
ally
lim
ited
to
ents
in s
hallo
w w
ater
zon
es a
nd lo
w
ntra
tions
.
bent
s ca
n be
use
d as
sed
imen
t m
ents
for i
n si
tu tr
eatm
ent o
f CO
Is.
on o
f met
als
and
orga
nics
can
take
pla
ce
aneo
usly
with
a s
uita
ble
com
bina
ion
of
ts.
Site
Estu
ary
App
licab
ility
to S
ite
Effe
ctiv
enes
s is
unc
erta
in fo
r m
etal
s. C
hem
ical
add
ition
may
cr
eate
toxi
c co
nditi
ons.
Can
be
effe
ctiv
e fo
r PA
Hs,
but
not
lik
ely
effe
ctiv
e fo
r met
als.
Ran
king
R
etai
ned
f C
onsi
dera
t
No
Effe
ctiv
enes
s
N
ot p
rove
n sa
fe a
nd e
ffect
ive
for
sedi
men
t site
s.
Met
als
are
not e
asily
rem
oved
by
bior
emed
iatio
n.
Suc
cess
dep
ends
on
tem
pera
ture
, pH
, ox
ygen
, nut
rient
ava
ilabi
lity,
bi
oava
ilabi
lity,
and
toxi
city
of e
nd
prod
ucts
, whi
ch v
ary
by s
ite a
nd a
re
diffi
cult
to c
ontro
l ins
itu.
Tim
e fra
me
diffi
cult
to p
redi
ct.
Impl
emen
tabi
lity
zIm
plem
enta
tion
invo
lves
pla
ntin
g an
d in
som
e ca
ses
harv
estin
g, w
ith li
ttle
disr
uptio
n to
he
site
.
S
orbe
nt a
men
dmen
ts c
an b
e de
liver
ed to
the
sedi
men
t in
he fo
rm
of p
elle
ts h
at a
re d
ense
eno
ugh
to
sink
thro
ugh
the
wat
er c
olum
n an
d ar
e re
sist
ant t
o re
-sus
pens
ion
whi
le
bein
g w
orke
d in
to th
e se
dim
ents
.
Pilo
t stu
dies
wou
ld b
e re
quire
d to
de
term
ine
the
effe
ctiv
enes
s of
sp
ecifi
c ox
idan
ts fo
r Site
CO
Is.
Bio
rem
edia
tion
is e
asily
impl
emen
ted
with
sha
llow
impa
cts,
but
bec
omes
m
ore
diffi
cult
with
dee
p im
pact
s.
B
ench
-sca
le a
nd p
ilot-s
cale
test
ing
requ
ired
to d
eter
min
e th
e ty
pe,
conc
entra
tion
and
quan
titie
s of
ox
idan
t and
am
endm
ents
nee
ded.
S
peci
aliz
ed e
quip
men
t is
likel
y re
quire
d fo
r inj
ectio
n of
che
mic
als.
Rela
tive
Cost
$$
Prim
ary
cost
s ar
e pu
rcha
sing
and
pl
antin
g ap
plic
able
spe
cies
. M
onito
ring
may
als
o be
requ
ired.
$$
The
mai
n co
sts
incl
ude
the
adso
rben
t m
ater
ial,
and
a m
etho
d fo
r dep
ositi
ng
it on
the
surfa
ce s
edim
ent.
Mon
itorin
g m
ay a
lso
be re
quire
d.
Cos
ts in
clud
e be
nch-
or p
ilot-s
cale
te
sts
to d
eter
min
e ef
fect
iven
ess,
ox
idan
ts fo
r inj
ectio
n, a
nd a
del
iver
y sy
stem
. M
onito
ring
may
als
o be
re
quire
d.
$$$
Cos
ts o
f enh
ance
d bi
orem
edia
tion
are
rela
tivel
y lo
w, b
ut s
ever
al tr
eatm
ents
an
d ex
tens
ive
mon
itorin
g m
ay b
e re
quire
d.
$$
Cos
ts in
clud
e be
nch-
or p
ilot-s
cale
te
sts.
Mon
itorin
g m
ay b
e re
quire
d.
$$$
Upl
and
Estu
ary
No
No
Upl
and
Estu
ary
Wou
ld re
quire
trea
tmen
t of l
arge
ar
eas.
Pla
n in
g re
stor
atio
n m
easu
res
to
rest
ore
habi
tat m
ay c
ontri
bute
to
natu
ral r
ecov
ery.
May
be
usef
ul a
s a
capp
ing
or
EN
R a
men
dmen
t in
the
area
s of
th
e de
lta w
here
impa
cted
se
dim
ent i
s at
the
surfa
ce a
nd
wou
ld b
e in
dire
ct c
onta
ct w
ith
amen
dmen
ts.
Lim
ited
effe
ctiv
enes
s fo
r Site
C
OIs
.
P
AH
deg
rada
tion
can
occu
r und
er b
oth
deni
trify
ing
and
sulfa
te-re
duci
ng
anae
robi
c co
nditi
ons.
Effe
ctiv
enes
s fo
r met
als
is h
ighl
y de
pend
ent o
n si
te
cond
i ion
s.
A
dditi
on o
f che
mic
als
may
form
toxi
c co
ndi i
ons
for b
enth
ic o
r aqu
atic
or
gani
sms.
No
No
Upl
and
Estu
ary/
U
plan
d
Estu
ary
C
hem
ical
oxi
datio
n ha
s lim
ited
dem
onst
rate
d ef
fect
iven
ess
for P
AH
s.
Effe
ctiv
enes
s fo
r tre
atin
g si
te m
etal
s is
no
t kno
wn,
but
dep
ends
on
the
spec
ific
cons
titue
nt.
O
nly
effe
ctiv
e w
here
CO
Is a
re n
ear
he
surfa
ce a
t res
idua
l con
cent
ratio
ns.
Rem
edia
tion
time
fram
e is
long
.
A
ctiv
ated
car
bon
is n
ot e
ffect
ive
for
met
als,
but
may
be
impr
egna
ted
with
io
n ex
chan
ge m
ater
ials
to e
nhan
ce
met
al a
dsor
ptio
n. H
owev
er, t
his
coul
d af
fect
the
carb
on's
cap
acity
for
orga
nics
abs
orpt
ion.
No
No
No
vene
ss
Impl
emen
tabi
lity
Rel
ativ
e C
ost
e te
chno
logy
R
eadi
ly im
plem
ente
d
cond
ition
s Im
plem
enta
ble,
requ
ires
tech
nica
l kno
wle
dge
ome
CO
Is o
r Site
are
as
Diff
icul
t to
impl
emen
t
ng S
MG
s or
PR
Gs
Not
impl
emen
tabl
e at
the
site
$ $$
$$$
Low
Mod
erat
e
Med
ium
-Hig
h
Hig
h $$
$$
atio
n Gu
idan
ce fo
r Haz
ardo
us W
aste
Site
s," E
PA-5
40-R
-05-
012,
OSW
ER 9
355.
0-85
, Was
hing
ton,
DC.
Sup
erfu
nd S
ites,"
EPA
-542
-R-0
0-01
0, O
SWER
510
2G, W
ashi
ngto
n, D
C.
umen
t," E
PA 9
05-B
94-0
03. C
hica
go, I
ll.: G
reat
Lak
es N
atio
nal P
rogr
am O
ffice
.
2002
. "Re
med
iatio
n Te
chno
logi
es S
cree
ning
Mat
rix a
nd R
efer
ence
Gui
de, 4
th E
ditio
n,"
Avai
labl
e on
line
at: h
ttp:
//w
ww
.frtr
.gov
/mat
rix2/
top_
page
.htm
l
dim
ents
with
Rea
ctiv
e M
ater
ials.
J.T.
Olsa
ta. P
roce
edin
gs o
f Por
ts 2
007:
30
Year
s of S
harin
g Id
eas 1
977-
2007
". A
mer
ican
Soc
iety
of C
ivil
Engi
neer
s (AS
CE).
Mar
ch 2
5-28
, 200
7.
e e t
Des
crip
tio
n
the
Unn
amed
Cre
ek s
trea
m
dire
ct fl
ow a
way
from
impa
cted
to
con
trol
sed
imen
t tra
nspo
rt u
sing
m
ilar
to a
nat
ural
str
eam
cha
nnel
. e
liner
mat
eria
ls a
nd g
eote
xtile
s fo
r on
trol
.
lver
t pip
e or
oth
er s
truc
ture
to c
arry
or
thro
ugh
a im
pact
ed a
rea.
ll or
par
t of t
he c
hann
el a
way
from
re
a.
wat
erin
g re
lies
on n
atur
al
n an
d dr
aina
ge to
rem
ove
moi
stur
e ed
imen
t. D
rain
age
may
be
driv
en
or a
ssis
ted
with
a v
acuu
m p
ump.
w
ater
ing
may
occ
ur in
CD
Fs,
nk
s, o
r te
mpo
rary
an
dlin
g fa
cilit
ies.
sedi
men
ts to
pro
mot
e dr
aina
ge,
sed
imen
ts w
ith e
xcav
atio
n ca
n en
hanc
e pa
ssiv
e de
wat
erin
g.
edim
ents
are
mix
ed w
ith
nts
such
as
slag
s or
cem
entit
ious
o
rem
ove
moi
stur
e an
d im
prov
e
nd s
tabi
lity.
slur
ry fr
om h
ydra
ulic
dre
dgin
g is
to
the
geot
extil
e tu
be a
nd fi
ltere
d ex
tile
fabr
ic. S
edim
ent i
s re
tain
ed
geot
extil
e tu
be, w
hile
free
liqu
ids
gh th
e ex
terio
r of
the
tube
.
l dew
ater
ing
tech
nolo
gies
incl
ude
e fil
ters
, pre
sses
, cen
trifu
ges
or
pmen
t to
sque
eze,
pre
ss, o
r dr
aw
dred
ged
sed
imen
t.
hat c
ontin
uous
ly p
roce
sses
the
a hy
drau
lic d
redg
e an
d se
para
tes
pile
s of
deb
ris; s
hells
; and
gra
vel,
fines
. Inc
lude
s po
lym
er a
dditi
on
atio
n, w
hich
may
rem
ove
som
e
s us
e m
icro
bial
act
ivity
to d
egra
de
nstit
uent
s in
wat
er.
Ap
plic
abili
ty t
o S
ite
Som
e de
gree
of s
urfa
ce w
ater
en
gine
erin
g w
ill b
e ne
cess
ary
for
any
alte
rnat
ive
exce
pt fo
r no
ac
tion.
Upl
and
area
s ar
e av
aila
ble
at th
e si
te th
at c
ould
ser
ve a
s a
pass
ive
dew
ater
ing
area
.
If a
CD
F is
con
stru
cted
, sed
imen
t re
wor
king
cou
ld b
e pe
rfor
med
w
ithin
the
CD
F.
Cou
ld b
e us
ed to
enh
ance
de
wat
erin
g in
con
junc
tion
with
se
dim
ent r
ewor
king
.
App
licab
le to
hyd
raul
ic d
redg
ing,
w
hich
is n
ot r
etai
ned
for
alte
rnat
ives
for
the
Site
.
Diff
icul
t to
prod
uce
requ
ired
hom
ogen
eous
was
te s
trea
m w
ith
mec
hani
cal d
redg
ing
met
hods
an
d si
te s
edim
ents
.
Onl
y su
itabl
e fo
r hy
drau
lic
dred
ging
met
hods
, whi
ch a
re n
ot
reta
ined
.
Not
effe
ctiv
e at
rem
ovin
g m
etal
s.
Ran
kin
g
Ret
a
in A
Eff
ecti
ven
ess
Hig
hly
effe
ctiv
e, w
ell e
stab
lishe
d m
etho
ds fo
r m
anag
ing
surf
ace
wat
er fl
ow a
nd d
iver
sion
P
assi
vely
dew
ater
ed s
edim
ents
may
not
hav
e lo
w e
noug
h w
ater
con
tent
for
land
fill d
ispo
sal,
so
supp
lem
enta
l tec
hnol
ogie
s m
ay b
e re
quire
d.
CD
F v
olum
e m
ust b
e de
sign
ed to
acc
ount
for
pass
ive
dew
ater
ing
resi
denc
e tim
e.
S
edim
ent m
ixin
g an
d re
wor
king
wou
ld fa
cilit
ate
a tim
elie
r an
d m
ore
com
plet
e de
wat
erin
g.
E
ffect
iven
ess
of a
men
dmen
ts d
epen
d on
the
moi
stur
e co
nten
t of r
emov
ed s
edim
ent.
Pre
-tre
atm
ent d
ewat
erin
g m
ay b
e ne
eded
for
max
imum
effe
ctiv
enes
s an
d to
ach
ieve
des
ired
geot
echn
ical
pro
pert
ies.
A
pplic
able
to h
ydra
ulic
dre
dgin
g.
For
fine
gra
ined
sed
imen
t (si
lt an
d pe
at fr
om
Spi
rit L
ake)
, pol
ymer
add
ition
is u
sual
ly n
eede
d to
faci
litat
e de
wat
erin
g.
Tre
atab
ility
test
s in
dica
te fi
ltrat
e w
ould
nee
d tr
eatm
ent t
o m
eet w
ater
qua
lity
crite
ria.
G
ener
ally
wor
ks b
est w
ith a
hom
ogen
eous
was
te
stre
am, s
o te
mpo
rary
sto
rage
in a
lago
on o
r ta
nk
wou
ld b
e re
quire
d (3
).
Sel
ectio
n of
spe
cific
mec
hani
cal d
ewat
erin
g eq
uipm
ent d
epen
ds o
n tr
eatm
ent o
r di
spos
al
met
hods
that
follo
w.
A
pplic
able
to h
ydra
ulic
dre
dgin
g m
etho
ds.
Pilo
t sca
le te
stin
g m
ay b
e ne
eded
to e
valu
ate
effe
ctiv
enes
s fo
r si
te s
peci
fic c
ondi
tions
.
∅ B
iore
acto
rs h
ave
ofte
n be
en u
sed
to e
ffect
ivel
y tr
eat P
AH
s, b
ut w
ould
not
be
effe
ctiv
e fo
r m
etal
s.
z
Imp
lem
enta
bili
ty
Hig
hly
impl
emen
tabl
e us
ing
stan
dard
des
ign
and
cons
truc
tion
met
hods
. P
erm
ittin
g m
ay b
e ne
cess
ary
for
dist
urbi
ng w
etla
nds
and
alte
ring
stor
m
wat
er fl
ow.
S
igni
fican
t foo
tprin
t req
uire
d fo
r co
nstr
uctio
n of
la
goon
s or
a C
DF
.
Tim
e fr
ames
for
pass
ive
dew
ater
ing
likel
y lo
nger
th
an fo
r m
echa
nica
l dew
ater
ing.
With
a p
rope
r C
DF
des
ign
pass
ive
met
hods
may
be
easi
ly s
uppl
emen
ted
with
oth
er d
ewat
erin
g te
chno
logi
es.
M
ixin
g an
d re
wor
king
sed
imen
ts w
ould
dec
reas
e tim
e ne
eded
to d
ewat
er w
ith p
assi
ve m
etho
ds.
Rew
orki
ng a
nd m
ixin
g co
uld
be d
one
with
sta
ndar
d ex
cava
tion
equi
pmen
t alre
ady
requ
ired
for
the
proj
ect.
W
ould
req
uire
sta
ging
, mix
ing,
and
cur
ing
area
s.
How
ever
, the
pro
cess
can
be
com
plet
ed in
a
rela
tivel
y sh
ort t
ime
fram
e.
Am
endm
ent a
dditi
on c
reat
es a
gre
ater
vol
ume
and
mas
s, w
hich
nee
ds to
be
cons
ider
ed in
dis
posa
l op
tions
.
W
ould
req
uire
a s
tagi
ng lo
catio
n if
tran
spor
ted
to
land
fill.
Dew
ater
ing
dura
tion
likel
y to
be
shor
ter
than
for
pass
ive
dew
ater
ing
but l
onge
r th
an m
echa
nica
l.
F
aste
r th
an p
assi
ve d
ewat
erin
g an
d re
quire
s le
ss
spac
e. P
rodu
ctio
n ra
tes
depe
nd o
n si
ze a
nd q
ualit
y of
the
dew
ater
ing
devi
ce a
nd o
n th
e so
lids
cont
ent
of th
e in
put s
trea
m.
T
he c
ompl
ete
syst
em is
mob
ile a
nd h
as a
rel
ativ
ely
smal
l foo
tprin
t.
∅ T
his
is a
long
-ter
m te
chno
logy
that
can
take
sev
eral
ye
ars
to b
ring
conc
entr
atio
ns o
f CO
Is to
acc
epta
ble
leve
ls (
4). R
esid
uals
from
the
slud
ge p
roce
ss a
lso
requ
ire tr
eatm
ent o
r di
spos
al.
z
Rel
ativ
e C
ost
Dep
ends
hig
hly
on th
e de
sign
.
ΨΨ
Cos
ts to
con
side
r in
clud
e co
nstr
uctio
n of
a
dew
ater
ing
faci
lity
or a
dequ
atel
y si
zed
CD
F.
ΨΨ
Cos
t sav
ings
are
exp
ecte
d ov
er p
assi
ve
dew
ater
ing
alon
e du
e to
tim
e sa
ved.
ΨΨ
Cos
ts in
clud
e am
endm
ent m
ater
ials
and
m
ixin
g eq
uipm
ent.
Cos
ts in
crea
se w
ith
incr
ease
d m
oist
ure
cont
ent.
Bot
h th
e ad
ditio
n ra
te a
nd th
e bu
lkin
g fa
ctor
of t
reat
ed m
ater
ial
shou
ld b
e co
nsid
ered
whe
n ev
alua
ting
cost
s of
am
endm
ent m
ater
ial.
ΨΨΨ
Cos
ts in
clud
e flo
ccul
ent a
nd c
oagu
lant
m
ater
ials
, cos
t of g
eote
xtile
tube
s an
d co
nstr
uctio
n of
sta
ging
are
a.
ΨΨΨΨ
C
osts
of m
echa
nica
l dew
ater
ing
are
gene
rally
hi
gher
than
pas
sive
dew
ater
ing
due
to th
e en
ergy
and
equ
ipm
ent r
equi
rem
ent.
ΨΨΨ
Exa
ct c
ost w
ould
dep
end
on s
ite-s
peci
fic
trea
tmen
t nee
ds.
ΨΨ
Cos
ts in
clud
e eq
uipm
ent,
ener
gy fo
r pu
mpi
ng
and
agita
tion,
and
slu
dge
mat
eria
l. C
ost i
s af
fect
ed b
y C
OD
of t
he w
ater
and
the
need
fo
r pH
adj
ustm
ent.
ΨΨ
c t e
Des
crip
tio
n
ove
solid
s an
d se
dim
ents
from
r,
als
o re
mov
ing
abso
rbed
CO
Is
aste
str
eam
. F
locc
ulan
ts m
ay b
e he
was
te s
trea
m to
faci
litat
e so
lids
umpi
ng w
ater
thro
ugh
a ve
ssel
gr
anul
ar a
ctiv
ated
car
bon
(GA
C),
, o
r an
othe
r ad
sorb
ent m
ater
ial;
ompo
unds
to a
dsor
b to
its
surf
ace.
oxid
atio
n us
es U
V li
ght a
nd th
e st
rong
oxi
dize
rs to
des
troy
org
anic
s
in w
ater
.
Ap
plic
abili
ty t
o S
ite
Filt
ratio
n is
a s
tand
ard
met
hod
for
wat
er tr
eatm
ent a
nd w
ould
be
effe
ctiv
e at
rem
ovin
g si
te C
OIs
so
rbed
to s
uspe
nded
sed
imen
ts
in th
e w
aste
str
eam
.
Con
vent
iona
l abs
orpt
ive
mat
eria
ls
wou
ld r
emov
e P
AH
s.
Not
effe
ctiv
e at
rem
ovin
g m
etal
s.
Ran
kin
g
Eff
ecti
ven
ess
z F
ilter
s ca
n be
sel
ecte
d ba
sed
on th
e re
quire
d pa
rtic
ulat
e si
ze.
Tre
atab
ility
stu
dy in
dica
ted
CO
Is in
CD
F e
fflue
nt
likel
y as
soci
ated
with
sus
pend
ed s
edim
ent,
so
filtr
atio
n m
ay b
e ef
fect
ive
at r
educ
ing
the
CO
I co
ncen
trat
ion.
A
ctiv
ated
car
bon
vess
els
are
appr
opria
te fo
r tr
eatin
g P
AH
s.
Act
ivat
ed a
lum
ina,
fora
ge s
pong
es, l
igni
n ad
sorp
tion/
sorp
tive
clay
s ar
e m
ore
effe
ctiv
e fo
r th
e re
mov
al o
f ino
rgan
ics
and
heav
y m
etal
s (4
).
The
pre
senc
e of
mul
tiple
con
stitu
ents
can
impa
ct
the
perf
orm
ance
of a
ctiv
ated
car
bon
syst
ems.
A
dvan
ced
oxid
atio
n is
app
licab
le fo
r tr
eatin
g m
ost o
rgan
ics,
incl
udin
g P
AH
s, b
ut m
ay n
ot b
e ef
fect
ive
for
the
trea
tmen
t of m
etal
s.
Imp
lem
enta
bili
ty
F
iltra
tion
is a
wid
ely
used
met
hod
for
wat
er
trea
tmen
t.
Sel
ectio
n of
the
filtr
atio
n m
etho
ds a
nd ty
pe r
equi
res
engi
neer
ing
desi
gn a
nd s
ite s
peci
fic k
now
ledg
e of
th
e w
aste
str
eam
.
Li
quid
ads
orpt
ion
syst
ems
are
wid
ely
avai
labl
e, h
ave
a re
lativ
ely
smal
l foo
tprin
t, an
d re
quire
a r
elat
ivel
y sh
ort t
imef
ram
e fo
r tr
eatm
ent.
A
dvan
ced
oxid
atio
n sy
stem
s ar
e w
idel
y av
aila
ble,
ha
ve a
rel
ativ
ely
smal
l foo
tprin
t, an
d re
quire
a
rela
tivel
y sh
ort t
imef
ram
e fo
r tr
eatm
ent.
Han
dlin
g an
d st
orag
e of
oxi
dize
rs w
ould
req
uire
sp
ecia
l saf
ety
prec
autio
ns.
Rel
ativ
e C
ost
ΨΨΨ
Cos
ts d
epen
d on
cha
nge
out f
requ
ency
of
filtr
atio
n m
ater
ial.
ΨΨΨ
Cos
ts in
clud
e ac
tivat
ed c
arbo
n, o
r ot
her
adso
rben
t ves
sels
. T
he a
dsor
bent
mus
t be
rech
arge
d or
rep
lace
d pe
riodi
cally
. P
ower
is
requ
ired
for
pum
ping
.
ΨΨΨΨ
C
osts
may
be
high
er b
ecau
se o
f ene
rgy
requ
irem
ents
to p
ower
UV
ligh
ts.
Ret
a
in A
Low
Mod
erat
e
Med
ium
-Hig
h
Hig
h
ess
Imp
lem
enta
bili
ty
Rel
ativ
e C
ost
chno
logy
R
eadi
ly im
plem
ente
d
nditi
ons
Im
plem
enta
ble,
req
uire
s
tech
nica
l kno
wle
dge
CO
Is o
r S
ite a
reas
D
iffic
ult t
o im
plem
ent
SM
Gs
or P
RG
s
Not
impl
emen
tabl
e at
the
site
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ĚŝƚŝŽŶΗ ǀĂŝůĂďůĞ ŽŶůŝŶĞ Ăƚ ŚƚƚƉǁǁǁĨƌƚƌŐŽǀŵĂƚƌŝdžϮƚŽƉͺƉĂŐĞŚƚŵů
-- ----
-- ----
----
----
----
----
--
----
----
----
----
--
----
----
--
----
----
----
----
----
----
----
--
----
----
--
----
----
----
----
----
----
----
----
----
--
0 0
287,
000
354,
000
454,
000
648,
000
616,
000
648,
000
327,
000
1,13
9,00
0
Alte
rnat
ive
1 Al
tern
ativ
e 2
Alte
rnat
ive
3 Al
tern
ativ
e 4
Alte
rnat
ive
5 Al
tern
ativ
e 6
Alte
rnat
ive
7 Al
tern
ativ
e 8
Alte
rnat
ive
9 Al
tern
ativ
e 10
172
57
77
78
91
91
91
121
121
30
30
30
30
30
30
30
30
47
37
37
37
28
14
22
22
22
57
36
42
46
31
23
23
34
F Ca
p
29
29
0 21
9 18
1 18
1 18
7 19
6 19
6 19
6 19
6 20
7
Alte
rnat
ive
1 Al
tern
ativ
e 2
Alte
rnat
ive
3 Al
tern
ativ
e 4
Alte
rnat
ive
5 Al
tern
ativ
e 6
Alte
rnat
ive
7 Al
tern
ativ
e 8
Alte
rnat
ive
9 Al
tern
ativ
e 10
0 -4
8 -1
1 9
10
20
20
20
7
Alte
rnat
ive
1 Al
tern
ativ
e 2
Alte
rnat
ive
3 Al
tern
ativ
e 4
Alte
rnat
ive
5 Al
tern
ativ
e 6
Alte
rnat
ive
7 Al
tern
ativ
e 8
Alte
rnat
ive
9 Al
tern
ativ
e 10
4 8
9 19
6
6 20
9
14
13
25
25
25
25
25
56
26
m p p
c o c l
escr
ipti
on
olve
s pl
acem
ent o
f a r
emed
ial c
ap o
ver
port
ions
of
ed C
reek
wou
ld b
e re
-rou
ted
to d
isch
arge
into
the
on o
f Wire
Mill
Del
ta.
edim
ents
from
the
Upl
and
Site
and
Est
uary
Site
with
U
-M D
elta
into
the
estu
ary.
The
alte
rnat
ive
also
ea
s on
the
Upl
and
Site
and
pla
cem
ent o
f a
n of
the
Est
uary
Site
. Unn
amed
Cre
ek w
ould
be
ed to
dis
char
ge in
to th
e fo
rmer
wat
er in
take
are
a in
uld
incl
ude
cons
truc
tion
of a
sm
all b
ase-
flow
du
ring
high
flow
con
ditio
ns).
tern
ativ
e 3
exce
pt th
at th
e ex
tent
of t
he C
DF
is
al w
ould
be
rem
oved
from
the
estu
ary
in th
e ar
ea
land
Site
and
pla
cem
ent o
f a r
emed
ial c
ap o
r E
NR
uld
incl
ude
cons
truc
tion
of a
sm
all b
ase-
flow
du
ring
high
flow
con
ditio
ns).
e dim
ents
from
the
Upl
and
Site
and
Est
uary
Site
with
a
port
ion
of O
U-M
Del
ta in
to th
e E
stua
ry S
ite. T
he
es a
n op
en w
ater
bay
. A s
mal
l CD
F w
ould
als
o be
land
Site
and
pla
cem
ent o
f a r
emed
ial c
ap o
r E
NR
uld
incl
ude
cons
truc
tion
of a
sm
all b
ase-
flow
du
ring
high
flow
con
ditio
ns)
and
disc
harg
e of
edim
ents
from
the
Upl
and
Site
and
Est
uary
Site
with
a
port
ion
of O
U-M
Upl
and
and
OU
-M D
elta
and
into
E
stua
ry S
ite w
ould
be
plac
ed in
the
Est
uary
por
tion
e w
ould
be
plac
ed in
the
Upl
and
port
ion
of th
e C
DF
. lte
red
bay
in O
U-M
and
the
estu
ary.
Bec
ause
the
an in
Alte
rnat
ive
5.
ener
ally
the
sam
e as
in A
ltern
ativ
e 5.
edim
ents
from
the
Upl
and
Site
and
Est
uary
Site
with
en
tirel
y w
ithin
the
Upl
and
site
. A r
emed
ial c
ap w
ould
t-
side
of t
he O
U-M
Del
ta. R
emov
al o
f im
pact
ed
Del
ta w
ould
cre
ate
a sh
allo
w s
helte
red
bay.
sto
rmw
ater
cha
lleng
es th
at w
ould
req
uire
w
ill r
equi
re e
xten
sive
soi
l sta
biliz
atio
n, r
ipra
p ag
ains
t a la
rge
flood
eve
nt th
at w
ill im
pact
the
OU
-I
appi
ng o
f im
pact
ed s
edim
ents
in p
ortio
ns o
f the
Up
lan
d R
AO
s an
d C
on
sid
erat
ion
s •
Pro
tect
hu
man
hea
lth
an
d t
he
envi
ron
men
t •
Pro
vid
e a
stab
le w
ater
co
urs
e fo
r st
orm
wat
er
con
veya
nce
an
d d
isch
arg
e •
Pre
serv
e ar
eas
for
eco
no
mic
dev
elo
pm
ent
Est
uar
y R
AO
s an
d C
on
sid
erat
ion
s •
Pro
tect
hu
man
hea
lth
an
d t
he
envi
ron
men
t •
Red
uce
ben
efic
ial u
se im
pai
rmen
ts f
or
St.
Lo
uis
R
iver
Are
a o
f C
on
cern
•
Imp
rove
hab
itat
(b
ette
rmen
t)
Low
-Med
ium
- 4
-
Wou
ld b
e ef
fect
ive
at p
rote
ctio
n of
hum
an h
ealth
and
env
ironm
ent a
s a
resu
lt of
phy
sica
l bar
rier,
but
wou
ld
not r
emov
e an
y im
pact
ed m
ater
ial.
- W
ould
be
effe
ctiv
e at
ach
ievi
ng R
AO
s an
d C
onsi
dera
tions
, with
the
exce
ptio
n th
at it
wou
ld r
esul
t in
the
loss
of
ope
n w
ater
hab
itat.
Eff
ecti
ven
ess
of
Ach
ievi
ng
RA
Os
and
Co
nsi
der
atio
ns
NA
- c
urre
nt c
ondi
tions
N
A
Med
ium
- 3
-
Larg
e vo
lum
e of
cap
ping
mat
eria
l is
nece
ssar
y;
how
ever
, tra
ditio
nal e
arth
wor
k an
d su
baqu
eous
ca
ppin
g eq
uipm
ent c
ould
be
used
. -C
onst
ruct
ion
of th
e W
ire M
ill d
isch
arge
str
uctu
re
wou
ld b
e po
ssib
le, b
ut c
halle
ngin
g.
Imp
lem
enta
bili
ty
NA
Low
-Med
ium
- 2
Rel
ativ
e C
ost R
anki
ng: #
2
Rel
ativ
e C
ost
Rel
ativ
e R
anki
ng
s:
#1 =
low
est
cost
; #1
2 =
hig
hes
t co
st
NA
9
Scr
een
ing
Lev
el S
core
(su
m o
f E
ffec
tive
nes
s,
Imp
lem
enta
bili
ty, a
nd
Co
st
sco
res)
Low
-Med
ium
- 4
-
Wou
ld b
e ef
fect
ive
at p
rote
ctio
n of
hum
an h
ealth
and
env
ironm
ent a
s a
resu
lt of
cap
pla
cem
ent a
nd im
pact
ed
mat
eria
l rem
oval
, -
Wou
ld b
e ef
fect
ive
at a
chie
ving
RA
Os
and
Con
side
ratio
ns,
with
the
exce
ptio
n th
at it
wou
ld r
esul
t in
the
loss
of
ope
n w
ater
hab
itat.
Med
ium
- 3
-
Dre
dgin
g, s
ubaq
ueou
s ca
ppin
g an
d tr
aditi
onal
ea
rthw
ork
equi
pmen
t wou
ld b
e ne
cess
ary.
-C
onst
ruct
ion
of th
e W
ire M
ill d
isch
arge
str
uctu
re
wou
ld b
e po
ssib
le, b
ut c
halle
ngin
g.
Low
-Med
ium
- 2
Rel
ativ
e C
ost R
anki
ng: #
3
9
Med
ium
-Hig
h -
2 -
Wou
ld b
e ef
fect
ive
at p
rote
ctio
n of
hum
an h
ealth
and
env
ironm
ent a
s a
resu
lt of
cap
pla
cem
ent a
nd im
pact
ed
mat
eria
l rem
oval
. -
Wou
ld b
e ef
fect
ive
at a
chie
ving
all
RA
Os
and
Con
side
ratio
ns.
- R
esul
ts in
a n
et g
ain
of o
pen
wat
er a
s a
resu
lt of
rem
oval
from
the
Wire
Mill
pon
d; h
owev
er, s
igni
fican
t hab
itat
impr
ovem
ent i
s no
t a m
ajor
com
pone
nt.
Med
ium
- 3
-
Dre
dgin
g, s
ubaq
ueou
s ca
ppin
g a
nd tr
aditi
onal
ea
rthw
ork
equi
pmen
t wou
ld b
e ne
cess
ary.
-C
onst
ruct
ion
of th
e W
ire M
ill d
isch
arge
str
uctu
re
wou
ld b
e po
ssib
le, b
ut c
halle
ngin
g.
Low
-Med
ium
- 2
Rel
ativ
e C
ost R
anki
ng: #
4
7
Hig
h -
1 -
Wou
ld b
e ef
fect
ive
at p
rote
ctio
n of
hum
an h
ealth
and
env
ironm
ent a
s a
resu
lt of
cap
pla
cem
ent a
nd im
pact
ed
mat
eria
l rem
oval
. -
Wou
ld b
e ef
fect
ive
at a
chie
ving
all
RA
Os
and
Con
side
ratio
ns.
- S
igni
fican
t hab
itat b
ette
rmen
t wou
ld b
e ac
hiev
ed th
roug
h cr
eatio
n of
the
open
wat
er b
ay.
Hig
h -
1 -
Wou
ld b
e ef
fect
ive
at p
rote
ctio
n of
hum
an h
ealth
and
env
ironm
ent a
s a
resu
lt of
cap
pla
cem
ent a
nd im
pact
ed
mat
eria
l rem
oval
. -
Wou
ld b
e ef
fect
ive
at a
chie
ving
all
RA
Os
and
Con
side
ratio
ns.
- S
igni
fican
t hab
itat b
ette
rmen
t wou
ld b
e ac
hiev
ed th
roug
h cr
eatio
n of
a s
hallo
w s
helte
red
bay.
Hig
h -
1 -
Wou
ld b
e ef
fect
ive
at p
rote
ctio
n of
hum
an h
ealth
and
env
ironm
ent a
s a
resu
lt of
cap
pla
cem
ent a
nd im
pact
ed
mat
eria
l rem
oval
. -
Wou
ld b
e ef
fect
ive
at a
chie
ving
all
RA
Os
and
Con
side
ratio
ns.
- S
igni
fican
t hab
itat b
ette
rmen
t wou
ld b
e ac
hiev
ed th
roug
h cr
eatio
n of
a s
hallo
w s
helte
red
bay.
Med
ium
- 3
-
Dre
dgin
g, s
ubaq
ueou
s ca
ppin
g a
nd tr
aditi
onal
ea
rthw
ork
equi
pmen
t wou
ld b
e ne
cess
ary.
Med
ium
- 3
Rel
ativ
e C
ost R
anki
ng: #
6
7
Med
ium
- 3
-
Dre
dgin
g, s
ubaq
ueou
s ca
ppin
g an
d tr
aditi
onal
ea
rthw
ork
equi
pmen
t wou
ld b
e ne
cess
ary.
Med
ium
- 3
Rel
ativ
e C
ost R
anki
ng: #
8
7
Low
-Med
ium
- 4
-
Dre
dgin
g an
d tr
aditi
onal
ear
thw
ork
equi
pmen
t w
ould
be
nece
ssar
y.
- C
onst
ruct
ion
of C
DF
in O
U-I
cre
ates
add
ed
stor
mw
ater
man
agem
ent a
nd e
ngin
eerin
g ch
alle
nges
- ta
ll, s
teep
ber
ms
and
does
not
allo
w
for
stor
mw
ater
pon
ding
. -H
igh
flow
sto
rmw
ater
dis
char
ge e
vent
s w
ould
be
diff
icul
t to
acco
mm
odat
e in
this
alte
rnat
ive.
Med
ium
-Hig
h -
4
Rel
ativ
e C
ost R
anki
ng: #
10
9
Ad
dit
ion
al F
acto
rs
N
As
a re
sult
of c
ap p
lac
48 a
cres
of o
pen
wat
e
CD
F lo
cate
d in
OU
-M
CD
F is
pla
ced
on to
p o
Net
loss
of a
ppro
xim
at
wat
er.
CD
F is
pla
ced
on to
p o
Pla
cem
ent o
f exc
avat
e se
dim
ents
in a
CD
F th
es
tuar
y. C
DF
s ar
e pl
a O
U's
.
Ope
n w
ater
bay
(1
ft a
wat
er d
epth
than
sha
ll 5
ft av
g. d
epth
).
Less
ope
n w
ater
and
s
wat
er d
epth
than
Alte
r
Cre
atio
n of
sha
llow
sh
Pla
cem
ent o
f dre
dged
co
nstr
ucte
d w
ithin
the
estu
ary.
CD
Fs
are
pla
OU
's.
Cre
atio
n of
sha
llow
sh
plac
emen
t of d
redg
ed
Del
ta o
r th
e es
tuar
y. C
to
p of
exi
stin
g O
U's
.
Doe
s no
t allo
w fo
r st
o r
OU
-I a
rea,
cre
atin
g ch
co
ntro
l and
ban
k st
abi
and
long
-ter
m b
asis
.
r r
s r r t r
escr
ipti
on
that
mat
eria
l tha
t is
rem
oved
from
OU
-M D
elta
and
ed
bay
wou
ld b
e co
nsol
idat
ed o
n th
e sp
it-si
de o
f er
mat
eria
l wou
ld b
e pl
aced
in C
DF
s lo
cate
d w
ithin
w
ater
man
agem
ent a
ctio
ns w
ould
be
requ
ired;
on
stru
cted
and
per
mitt
ed th
an th
ose
in A
ltern
ativ
e 7.
eek,
from
OU
-J to
OU
-M U
plan
d w
ould
be
sim
ilar
to
capp
ing
of im
pact
ed s
edim
ents
in p
ortio
ns o
f the
all m
ater
ial i
s co
nsol
idat
ed in
an
upla
nd C
DF
. in
OU
-I, s
ince
less
tota
l sed
imen
t is
bein
g ia
l cap
is p
lace
d th
roug
hout
the
OU
-M D
elta
, d
bay.
capp
ing
of im
pact
ed s
edim
ents
in p
ortio
ns o
f the
sedi
men
ts fr
om th
e U
plan
d S
ite a
nd E
stua
ry S
ite
CD
F lo
cate
d in
the
pote
ntia
lly d
evel
opab
le a
rea
of
and
capp
ing
of im
pact
ed s
edim
ents
in p
ortio
ns o
f
nvol
ves
rem
oval
of a
ll se
dim
ents
that
exc
eed
Rem
oved
mat
eria
ls w
ould
be
depo
site
d in
a n
early
pa
ble
area
of t
he U
plan
d S
ite.
ough
the
CD
F w
ill in
clud
e a
final
cov
er.
s edi
men
ts fr
om th
e U
plan
d S
ite a
nd th
e E
stua
ry
Alte
rnat
ive
12 is
uni
que
from
oth
er a
ltern
ativ
es fo
r he
OU
-M D
elta
. (2)
Som
e re
mov
ed m
ater
ial w
ill b
e n
area
ref
erre
d to
as
the
"Bor
row
Site
." (
3) R
emov
al
n op
en w
ater
bay
that
is la
rger
than
oth
er
capp
ing
of im
pact
ed s
edim
ents
in p
ortio
ns o
f the
Scr
een
ing
Key
:
Up
lan
d R
AO
s an
d C
on
sid
erat
ion
s •
Pro
tect
hu
man
hea
lth
an
d t
he
envi
ron
men
t •
Pro
vid
e a
stab
le w
ater
co
urs
e fo
r st
orm
wat
er
con
veya
nce
an
d d
isch
arg
e •
Pre
serv
e ar
eas
for
eco
no
mic
dev
elo
pm
ent
Est
uar
y R
AO
s an
d C
on
sid
erat
ion
s •
Pro
tect
hu
man
hea
lth
an
d t
he
envi
ron
men
t •
Red
uce
ben
efic
ial u
se im
pai
rmen
ts f
or
St.
Lo
uis
R
iver
Are
a o
f C
on
cern
•
Imp
rove
hab
itat
(b
ette
rmen
t)
Eff
ecti
ven
ess
of
Ach
ievi
ng
RA
Os
and
Co
nsi
der
atio
ns
Hig
h -
1 -
Wou
ld b
e ef
fect
ive
at p
rote
ctio
n of
hum
an h
ealth
and
env
ironm
ent a
s a
resu
lt of
cap
pla
cem
ent a
nd im
pact
ed
mat
eria
l rem
oval
. -
Wou
ld b
e ef
fect
ive
at a
chie
ving
all
RA
Os
and
Con
side
ratio
ns.
- S
igni
fican
t hab
itat b
ette
rmen
t wou
ld b
e ac
hiev
ed th
roug
h cr
eatio
n of
a s
hallo
w s
helte
red
bay.
Imp
lem
enta
bili
ty
Rel
ativ
e C
ost
Rel
ativ
e R
anki
ng
s:
#1 =
low
est
cost
; #1
2 =
hig
hes
t co
st
Scr
een
ing
Lev
el S
core
(su
m o
f E
ffec
tive
nes
s,
Imp
lem
enta
bili
ty, a
nd
Co
st
sco
res)
Med
ium
- 3
-
Dre
dgin
g, s
ubaq
ueou
s ca
ppin
g a
nd tr
aditi
onal
ea
rthw
ork
equi
pmen
t wou
ld b
e ne
cess
ary.
Med
ium
- 3
Rel
ativ
e C
ost R
anki
ng: #
7
7
Med
ium
-Hig
h -
2 -
Wou
ld b
e ef
fect
ive
at p
rote
ctio
n of
hum
an h
ealth
and
env
ironm
ent a
s a
resu
lt of
cap
pla
cem
ent a
nd im
pact
ed
mat
eria
l rem
oval
. -
Wou
ld b
e ef
fect
ive
at a
chie
ving
all
RA
Os
and
Con
side
ratio
ns.
- R
esul
ts in
a n
et g
ain
of o
pen
wat
er a
s a
resu
lt of
Upl
and
sedi
men
t rem
oval
from
the
Wire
Mill
Del
ta; h
owev
er,
sign
ifica
nt h
abita
t im
prov
emen
t is
not a
maj
or c
ompo
nent
.
Low
-Med
ium
- 4
-
Dre
dgin
g, s
ubaq
ueou
s ca
ppin
g a
nd tr
aditi
onal
ea
rthw
ork
equi
pmen
t wou
ld b
e ne
cess
ary.
Med
ium
- 3
Rel
ativ
e C
ost R
anki
ng: #
5
9
Med
ium
- 3
-
Wou
ld b
e ef
fect
ive
at p
rote
ctio
n of
hum
an h
ealth
and
env
ironm
ent a
s a
resu
lt of
cap
pla
cem
ent a
nd im
pact
ed
mat
eria
l rem
oval
. -
Wou
ld b
e ef
fect
ive
at a
chie
ving
all
RA
Os
and
Con
side
ratio
ns e
xcep
t for
pre
serv
ing
area
s fo
r ec
onom
ic
bene
fit (
cons
truc
tion
of la
rge
CD
F in
Upl
and
Site
wou
ld e
limin
ate
poss
ibili
ty fo
r de
velo
pmen
t).
- R
esul
ts in
a n
et g
ain
of o
pen
wat
er a
s a
resu
lt of
Upl
and
Site
rem
oval
; how
ever
, sig
nific
ant h
abita
t im
prov
emen
t is
not a
maj
or c
ompo
nent
.
Low
-Med
ium
- 4
-
Dre
dgin
g, s
ubaq
ueou
s ca
ppin
g an
d tr
aditi
onal
ea
rthw
ork
equi
pmen
t wou
ld b
e ne
cess
ary.
-
Larg
e vo
lum
e of
sed
imen
t to
rem
ove
and
tran
spor
t to
Upl
and
CD
F.
- W
ould
cau
se a
hig
h de
gree
of d
isru
ptio
n to
the
Site
. -L
arge
vol
ume
of w
ater
to b
e tr
eate
d.
Hig
h -
5
Rel
ativ
e C
ost R
anki
ng: #
11
12
Med
ium
- 3
-
Wou
ld b
e ef
fect
ive
at p
rote
ctio
n of
hum
an h
ealth
and
env
ironm
ent a
s a
resu
lt of
cap
pla
cem
ent a
nd im
pact
ed
mat
eria
l rem
oval
. -
Wou
ld b
e ef
fect
ive
at a
chie
ving
all
RA
Os
and
Con
side
ratio
ns e
xcep
t for
pre
serv
ing
area
s fo
r ec
onom
ic
bene
fit (
cons
truc
tion
of la
rge
CD
F in
Upl
and
Site
wou
ld e
limin
ate
poss
ibili
ty fo
r de
velo
pmen
t).
Low
- 5
-
Dre
dgin
g an
d tr
aditi
onal
ear
thw
ork
equi
pmen
t w
ould
be
nece
ssar
y.
- V
ery
larg
e vo
lum
e of
sed
imen
t to
rem
ove
and
tran
spor
t. -
Wou
ld c
ause
a h
igh
degr
ee o
f dis
rupt
ion
to th
e S
ite.
-Ver
y la
rge
volu
me
of w
ater
to b
e tr
eate
d.
Hig
h -
5
Rel
ativ
e C
ost R
anki
ng: #
12
13
Med
ium
-Hig
h -
2 -
Wou
ld b
e ef
fect
ive
at p
rote
ctio
n of
hum
an h
ealth
and
env
ironm
ent a
s a
resu
lt of
cap
pla
cem
ent a
nd im
pact
ed
mat
eria
l rem
oval
. -
Sig
nific
ant h
abita
t bet
term
ent w
ould
be
achi
eved
thro
ugh
crea
tion
of th
e sh
allo
w s
helte
red
bay.
-
Wou
ld b
e ef
fect
ive
at a
chie
ving
all
RA
Os
and
Con
side
ratio
ns e
xcep
t for
pre
serv
ing
area
s fo
r ec
onom
ic
bene
fit (
cons
truc
tion
of la
rge
CD
F in
Upl
and
Site
wou
ld e
limin
ate
poss
ibili
ty fo
r de
velo
pmen
t).
Low
-Med
ium
- 4
-
Dre
dgin
g, s
ubaq
ueou
s ca
ppin
g a
nd tr
aditi
onal
ea
rthw
ork
equi
pmen
t wou
ld b
e ne
cess
ary.
-
Sed
imen
t wou
ld b
e tr
ansp
orte
d gr
eate
r di
stan
ces
than
in a
ll al
tern
ativ
es e
xcep
t for
A
ltern
ativ
es 1
0 an
d 11
. -
Con
solid
atio
n of
larg
e vo
lum
e of
sed
imen
t in
OU
-M U
plan
d C
DF
res
ults
in h
igh
berm
s.
Med
ium
-Hig
h -
4
Rel
ativ
e C
ost R
anki
ng: #
9
10
Ad
dit
ion
al F
acto
rs
Onl
y m
ater
ial t
hat i
s re
sh
allo
w s
helte
red
bay
the
OU
-M D
elta
and
e
is c
onso
lidat
ed to
geth
e on
top
of e
xist
ing
OU
's
Pla
cem
ent o
f im
pact
ed
CD
Fs.
CD
Fs
are
plac
e O
U's
.
Sig
nific
ant h
abita
t im
p m
ajor
com
pone
nt.
Ca
may
req
uire
wet
land
m
conv
eyan
ce a
cha
lleng
D
elta
.
Sig
nific
ant h
abita
t im
p m
ajor
com
pone
nt.
De
lost
due
to th
e co
nstr
u co
nsol
idat
ion
area
.
Dev
elop
able
upl
and
ar
cons
truc
tion
of a
n up
la
Mor
e ar
ea o
f ope
n w
a sh
allo
wer
ave
rage
wa t
sh
elte
red
bays
in o
the
No
plac
emen
t of r
emo
Del
ta.
CD
F c
onst
ruct
ed in
no
site
.
Eff
ecti
ven
ess
Imp
lem
enta
bili
ty
Co
st
Ove
rall
Sco
re
Hig
hest
Effe
ctiv
enes
s -
1 po
int
Hig
hest
Impl
emen
tabi
lity
- 1
poin
t Lo
wes
t Cos
t - 1
poi
nt
<4
Med
ium
-Hig
h E
ffect
iven
ess
- 2
poin
ts
Med
ium
-Hig
h Im
plem
enta
bilit
y -
2 po
ints
Lo
w-M
ediu
m C
ost -
2 p
oint
s 5-
7 po
ints
Med
ium
Effe
ctiv
enes
s -
3 po
ints
M
ediu
m Im
plem
enta
bilit
y -
3 po
ints
M
ediu
m C
ost -
3 p
oint
s 8-
10 p
oint
s
Low
-Med
ium
Effe
ctiv
enes
s -
4 po
ints
Lo
w-M
ediu
m Im
plem
enta
bilit
y -
4 po
ints
M
ediu
m-H
igh
Cos
t - 4
poi
nts
11-1
3 po
ints
Low
est E
ffect
iven
ess
- 5
poin
ts
Low
est I
mpl
emen
tabi
lity
- 5
poin
ts
Hig
hest
Cos
t - 5
poi
nts
>13
poi
nts
>ŽǁĞƐƚ ƐĐŽƌĞ
ŝƐ ƚŚĞ ŵŽƐƚ ĚĞƐŝƌĂďůĞ
Tabl
e 5-
3
EVAL
UATI
ON
CRI
TERI
A
Form
er U
. S. S
teel
Dul
uth
Wor
ks -
Spiri
t Lak
e Se
dim
ent S
ite
Sain
t Lou
is Ri
ver
Dulu
th, M
inne
sota
Cat
egor
y C
riter
ia
Des
crip
tion
Fact
ors
Con
side
red
Thre
shol
d C
riter
ia
Ove
rall
Pro
tect
ion
of H
uman
Hea
lth a
nd th
e E
nviro
nmen
t H
ow d
oes
the
alte
rnat
ive
achi
eve
and
mai
ntai
n pr
otec
tion
of h
uman
he
alth
and
the
envi
ronm
ent?
E
limin
atio
n, re
duct
ion,
or c
ontro
l of c
urre
nt a
nd p
oten
tial/f
utur
e ris
ks
from
dire
ct o
r ind
irect
exp
osur
e to
CO
Is b
y re
pres
enta
ive
indi
vidu
als
and
targ
eted
env
ironm
enta
l spe
cies
bas
ed o
n si
te s
peci
fic e
xpos
ure
scen
ario
s an
d si
te s
peci
fic u
nder
stan
ding
of C
OI f
ate
and
trans
port.
Com
plia
nce
with
Reg
ulat
ory
Req
uire
men
ts (A
RA
Rs)
H
ow d
oes
the
alte
rnat
ive
com
ply
with
app
licab
le re
gula
tory
re
quire
men
ts a
nd A
RA
Rs?
-
Rev
iew
and
und
erta
ndin
g of
the
requ
irem
ents
for c
ompl
ianc
e w
ith
actio
n-sp
ecifi
c, lo
catio
n-sp
ecifi
c an
d ch
emic
al s
peci
fic A
RA
Rs.
-
Com
plia
nce
wi h
oth
er c
riter
ia, a
dvis
orie
s an
d gu
idan
ce.
Bal
anci
ng C
riter
ia
Long
Ter
m E
ffect
iven
ess
and
Per
man
ence
Th
e fu
nctio
nal a
bilit
y of
the
com
plet
ed a
ctiv
ities
to m
aint
ain
prot
ectio
n of
hum
an h
ealth
and
the
envi
ronm
ent a
fter r
espo
nse
actio
ns h
ave
been
impl
emen
ted
by re
mov
al o
r des
truct
ion
of
mat
eria
ls c
onta
inin
g C
OIs
or e
ngin
eere
d ba
rrie
rs to
pro
hibi
t con
tact
w
ith m
ater
ials
con
tain
ing
CO
Is.
-M
agni
tude
of r
esid
ual r
isk.
-
Ade
quac
y an
d re
liabi
lity
of c
onta
inm
ent o
r con
trol s
yste
ms
incl
udin
g:
safe
ty fa
ctor
s fo
r eng
inee
red
barr
iers
; ope
ratio
n, m
aint
enan
ce, a
nd
mon
itorin
g of
pro
gram
s fo
r con
tain
men
t sys
tem
s; a
nd in
s itu
tiona
l m
easu
res
to m
aint
ain
and
repo
rt on
long
-term
act
iviti
es, a
s ne
cess
ary.
Red
uctio
n of
Tox
icity
and
Mob
ility
(Ove
rall
Ris
k)
Qua
ntiti
ativ
e as
sess
men
t of t
he m
ass
and/
or v
olum
e of
mat
eria
l th
at is
tran
sfor
med
, rem
oved
from
the
site
, or c
onta
ined
in a
m
anne
r tha
t pro
hibi
ts fu
ture
mig
ratio
n of
CO
Is o
r dire
ct o
r ind
irect
ex
posu
res.
-P
roce
ss u
sed
and
mat
eria
ls m
itiga
ted.
-
Exp
ecte
d re
duct
ions
in to
xici
ty, m
obili
ty a
nd v
olum
e.
-D
egre
e to
whi
ch th
e re
med
y re
duce
s pr
inci
pal
hrea
ts.
Sho
rt-Te
rm E
ffec
iven
ess
Con
side
ratio
n of
the
effe
ct o
f sec
onda
ry im
pact
s as
soci
ated
with
th
e im
plem
enta
tion
of a
n al
tern
ativ
e an
d th
eir r
elat
ed im
pact
s on
hu
man
hea
lth a
nd th
e en
viro
nmen
t nea
r the
site
dur
ing
cons
truct
ion
and
impl
emen
tatio
n of
a re
med
y an
d co
ntin
uing
unt
il th
e re
spon
se o
bjec
tives
hav
e be
en a
chie
ved.
-P
rote
c io
n of
the
loca
l com
mun
ity d
urin
g re
med
ial a
ctio
ns fr
om
pote
ntia
l env
ironm
enta
l im
pact
s in
clud
ing
dust
, noi
se, e
rosi
on,
incr
ease
d tra
ffic,
or o
ther
fact
ors.
-
Env
ironm
enta
l im
pact
s of
rem
edia
l act
ions
. -
Dur
a io
n of
rem
edia
l act
ions
.
Impl
emen
tabi
lity
Eva
luat
ion
of th
e te
chni
cal a
nd a
dmin
istra
tive
feas
ibili
ty o
f co
mpl
etin
g an
alte
rnat
ive
incl
udin
g th
e av
aila
bilit
y of
ser
vice
s,
mat
eria
ls, e
quip
men
t and
ski
lled
man
pow
er a
nd o
ther
reso
urce
s ne
eded
to s
ucce
ssfu
lly c
ompl
ete
the
Pro
ject
.
-A
bilit
y to
con
stru
ct a
nd o
pera
te th
e te
chno
logy
. -
Rel
iabi
lity
of h
e te
chno
logy
. -
Coo
rdin
atio
n w
ith o
ther
sta
keho
lder
s an
d ag
enci
es.
-C
apac
ity a
nd a
vaila
bilit
y of
nec
essa
ry e
quip
men
t and
spe
cial
ists
.
Cos
t A
n en
gine
erin
g es
timat
e of
the
likel
y ca
pita
l and
O&
M c
ost o
f eac
h al
tern
ativ
e, w
ith a
ppro
pria
te c
ontin
genc
ies
to m
atch
the
prel
imin
ary
natu
re o
f the
des
ign
wor
k co
mpl
eted
and
he
desi
gn w
ork
that
will
re
mai
n pr
ior t
o im
plem
entin
g th
e P
roje
ct.
- C
apita
l cos
ts.
-O
pera
ting
and
mai
nten
ance
cos
ts.
-P
erfo
rman
ce p
erio
d/du
ratio
n of
con
stru
ctio
n.
-P
ropo
rtion
ality
bet
wee
n th
e ris
k re
duct
ion
and
cost
of
he re
med
y.
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ent
Prin
cipl
e1
rly a
nd O
ften
.
cal G
over
nmen
ts, T
ribes
, and
Nat
ural
cept
ual S
ite M
odel
that
Con
side
rs
in a
Ris
k-Ba
sed
Fram
ewor
k.
umpt
ions
and
Unc
erta
intie
s er
izatio
n Da
ta a
nd S
ite M
odel
s.
t-Sp
ecifi
c, a
nd S
edim
ent-
Spec
ific
Risk
at
will
Ach
ieve
Ris
k-Ba
sed
Goal
s.
nup
Leve
ls a
re C
lear
ly T
ied
to R
isk
ss o
f Ins
titut
iona
l Con
trol
s and
miz
e Sh
ort-
term
Ris
ks w
hile
io
n.
r Sed
imen
t Rem
edia
tion
to A
sses
s ct
iven
ess.
Sum
mar
y
,
-Iden
tify
dire
ct a
nd in
dire
ct so
urce
s of s
igni
fican
t con
tam
inat
ion
to th
e se
dim
ents
und
er in
vest
igat
ion.
-A
sses
s whi
ch c
ontin
uing
sour
ces c
an b
e co
ntro
lled
and
by w
hat m
echa
nism
s.
-Eva
luat
e th
e po
tent
ial f
or fu
ture
reco
ntam
inat
ion
of se
dim
ents
whe
n se
lect
ing
a re
spon
se a
ctio
n.
-Ens
ure
early
and
mea
ning
ful c
omm
unity
invo
lvem
ent b
y pr
ovid
ing
com
mun
ity m
embe
rs w
ith n
eces
sary
tech
nica
l inf
orm
atio
n fo
r the
ir in
form
-Pro
vide
affe
cted
par
ties w
ith th
e sa
me
info
rmat
ion
used
by
the
deci
sion
mak
ers.
-In
clud
e al
l affe
cted
par
ties i
n th
e en
tire
deci
sion-
mak
ing
proc
ess t
o th
e ex
tent
pos
sible
. -A
llow
ade
quat
e tim
e fo
r eva
luat
ion
and
com
men
t on
the
info
rmat
ion
by a
ll pa
rtie
s.
-Com
mun
icat
e an
d co
ordi
nate
ear
ly to
ens
ure
the
mos
t rel
evan
t inf
orm
atio
n is
cons
ider
ed a
nd th
at th
ese
view
poin
ts a
re c
onsid
ered
in th
e re
-A c
once
ptua
l site
mod
el sh
ould
iden
tify
all k
now
n an
d su
spec
ted
sour
ces o
f con
tam
inat
ion.
The
type
s of c
onta
min
ants
and
affe
cted
med
ia, e
pa
thw
ays,
and
the
know
n or
pot
entia
l hum
an a
nd e
colo
gica
l rec
epto
rs th
at m
ay b
e th
reat
ened
. -P
repa
re th
e co
ncep
tual
site
mod
el e
arly
and
use
it to
gui
de si
te in
vest
igat
ions
and
dec
ision
mak
ing.
-U
pdat
e co
ncep
tual
site
mod
el w
hen
new
info
rmat
ion
beco
mes
ava
ilabl
e an
d un
ders
tand
ing
of th
e sit
e in
crea
ses.
-C
once
ptua
l site
mod
el is
esp
ecia
lly im
port
ant a
t sed
imen
t site
s for
und
erst
andi
ng th
e co
mpl
ex in
terr
elat
ions
hips
and
pot
entia
l for
cha
ngin
g c
-U
se a
risk
-bas
ed fr
amew
ork
or st
rate
gy fo
r rem
edy
eval
uatio
n an
d se
lect
ing
resp
onse
act
ions
app
ropr
iate
for t
he si
te.
-Use
an
itera
tive
appr
oach
that
inco
rpor
ates
test
ing
of h
ypot
hese
s/co
nclu
sions
and
fost
ers r
e-ev
alua
tion
of si
te a
ssum
ptio
ns a
s new
info
rmat
-Con
sider
the
bene
fits o
f pha
sing
rem
edia
tion
espe
cial
ly w
hen
early
act
ion
is ne
eded
to q
uick
ly re
duce
risk
s or c
ontr
ol th
e sp
read
of c
onta
min
-T
his f
ram
ewor
k sh
ould
not
be
used
to d
elay
a d
ecisi
on a
t a si
te if
suffi
cien
t inf
orm
atio
n is
avai
labl
e to
mak
e an
info
rmed
dec
ision
. -T
he a
mou
nt o
f site
spec
ific
data
requ
ired
and
com
plex
ity o
f mod
els u
sed
to su
ppor
t site
dec
ision
s sho
uld
depe
nd o
n th
e co
mpl
exity
of t
he si
t de
cisio
n.
-Cle
arly
des
crib
e th
e ba
sis fo
r all
mod
els u
sed
and
thei
r unc
erta
intie
s whe
n us
ing
the
pred
icte
d re
sults
to m
ake
a sit
e de
cisio
n.
-The
re is
no
pres
umpt
ive
rem
edy
for a
ny c
onta
min
ated
sedi
men
t site
s, re
gard
less
of t
he c
onta
min
ant o
r lev
el o
f risk
. -E
valu
ate
all r
emed
ies t
hat m
ay p
oten
tially
mee
t the
pro
ject
goa
ls/ob
ject
ives
prio
r to
sele
ctin
g th
e sit
e re
med
y.
-Rem
edie
s sho
uld
be e
valu
ated
on
a co
mpa
rativ
e ba
sis, c
onsid
erin
g al
l com
pone
nts o
f the
rem
edie
s, te
mpo
ral a
nd sp
atia
l asp
ects
of t
he si
te a
re
duct
ion
pote
ntia
lly a
chie
ved.
-A
t man
y sit
es, a
com
bina
tion
of o
ptio
ns w
ill b
e th
e m
ost e
ffect
ive
to m
anag
e ris
k.
-Whi
le it
is g
ener
ally
mor
e pr
actic
al to
use
mea
sure
s suc
h as
con
tam
inan
t con
cent
ratio
ns in
sedi
men
t to
iden
tify
area
s to
be re
med
iate
d, o
the
en
sure
hum
an h
ealth
and
/or e
colo
gica
l risk
redu
ctio
n go
als a
re b
eing
met
. -In
stitu
tiona
l con
trol
s are
ofte
n us
ed a
s a c
ompo
nent
of t
he re
med
ial d
ecisi
ons a
t sed
imen
t site
s to
limit
hum
an e
xpos
ures
and
to p
reve
nt fu
r re
dist
ribut
ion
until
rem
edia
l act
ion
obje
ctiv
es a
re m
et.
-Inst
itutio
nal c
ontr
ols m
ay n
ot b
e ef
fect
ive
in e
limin
atin
g or
sign
ifica
ntly
redu
cing
all
expo
sure
s.
-Con
sider
the
adva
ntag
es a
nd d
isadv
anta
ges o
f ava
ilabl
e op
tions
and
bal
ance
the
risks
, cos
ts a
nd b
enef
its o
f eac
h op
tion.
-Id
entif
y an
d co
nsid
er sh
ort-
term
and
long
-ter
m im
pact
s of e
ach
alte
rnat
ive
on so
ciet
al a
nd c
ultu
ral p
ract
ices
, as a
ppro
pria
te.
-Est
ablis
h a
phys
ical
, che
mic
al a
nd/o
r bio
logi
cal m
onito
ring
prog
ram
to d
eter
min
e if
risks
are
bei
ng m
itiga
ted
and
to e
valu
ate
rem
edy
effe
ctiv
-C
olle
ct b
asel
ine
data
for u
se in
com
parin
g an
d lo
ng-t
erm
rem
edy
effe
ctiv
enes
s.
-Iden
tify
long
term
mon
itorin
g in
dica
tors
that
are
use
d to
det
erm
ine
the
succ
ess o
f a re
med
y in
mee
ting
broa
der r
emed
ial o
bjec
tives
.
man Health Protection Mitigate the potential for direct contact with and/or incidental ingestion of, impacted soils and sediment. Addresses potential recreational and trespass user risks.
vironmental Protection Reduce the potential for unacceptable risk to ecological receptors.
mpliance with Regulatory Requirements (ARARs) mpliance with Applicable Regulatory Guidance x Meets the regulatory requirements of governing agencies.
mpliance with ARARs x Actions are permit-able by stakeholder agencies
g-Term Effectiveness and Permanence agnitude of Residual Risk x Remedy addresses residual risk to human health and the
environment. equacy and Reliability of Containment or Controls x Remedy is permanent and effective in the long-term.
uction of Toxicity and Mobility (Overall Risk) ocess Used and Materials Mitigated pected Reductions in Toxicity, Mobility and Volume pe and Quantity of Materials Remaining After Implementation gree to which the Remedy Reduces Principal Threats
rt-Term Effectiveness otection of Community during Remedial Actions vironmental Impacts of Remedial Actions ration of Remedial Actions
lementability ility to Construct and Operate the Technology iability of the Technology ordination with Other Stakeholders and Agencies pacity and Availability of Equipment and Specialists
t pital Costs ng-Term O&M Costs rformance Period
health and the environment. The actions of excavating and dredgin impacted soils/sediment and consolidating these materials within a M delta CDF will partially cover the greatest thickness of non-native sediment and reduce the footprint of impacted materials across the The complimentary actions of remedial capping and placement of a thin cover will eliminate direct human health exposure pathways an control the risk to ecological receptors.
Execution of Alternative 4 will address regulatory requirements by achieving Upland RAOs and Estuary SMGs.
The combination of removal, consolidation and capping of impacted and sediment will effectively mitigate residual risk by eliminating hu health and ecological exposure pathways in the FS areas of concern remedy is permanent, but will require long-term monitoring and O& maintain effectiveness of engineering controls. Institutional contro layered over engineering controls will address the future threat of disturbance to protective measures associated with this remedy. Diversion of storm water to the former plant water intake area will require engineered energy dissipation and armoring structures that require on-going maintenance. Alternative 4 will be effective in reducing the overall risk posed by C present in the Upland and Estuary areas of the Site. This alternative utilizes industry-proven methods for removal, consolidation and ca of impacted soil and sediment. The volume of impacted material w reduced through off-site disposal of characteristic hazardous lead-impacted soil from OU-Q. However, the future mobility of COI will eliminated through implementation of proposed engineering contro Implementation of Alternative 4 is not anticipated to have a signific adverse effect on the community or environment while constructio underway. Construction-related traffic will be moderate and proper protective measures will be implemented to eliminate exposure ris the community. Best management practices will be implemented d construction to minimize environmental impacts. The duration of Alternative 4 is consistent with Alternatives 6 and 8 and is expected encompass two years. Alternative 4 is implementable and will provide a reliable remedy to address risks posed by COCs present in the Upland and Estuary area the Site. The technology associated with this alternative is proven a there are no perceived capacity or availability issues with earth mov and dredging contractors who will perform the work. Placement of within the OU-M delta presents slightly increased logistical challeng associated with longer haul routes from some removal areas. Alternative 4 is identified as the lowest cost alternative advancing t detailed analysis. Long-term O&M is projected to be slightly higher Alternatives 6 and 8 because of maintenance of the concrete storm structures. The O&M costs are projected to be similar to Alternative but less than Alternative 7. The estimated two year duration of Alternative 4 construction is also consistent with Alternatives 6 and
man Health Protection Mitigate the potential for direct contact with and/or incidental ingestion of impacted soils and sediment. Addresses potential recreational and trespass user risks.
vironmental Protection Reduce the potential for unacceptable risk to ecological receptors.
mpliance with Regulatory Requirements (ARARs) mpliance with Applicable Regulatory Guidance x Meets the regulatory requirements of governing agencies.
mpliance with ARARs x Actions are permit-able by stakeholder agencies
g-Term Effectiveness and Permanence agnitude of Residual Risk x Remedy addresses residual risk to human health and the
environment. iability of Controls x Remedy is permanent and effective in the long-term.
uction of Toxicity and Mobility (Overall Risk) ocess Used and Materials Mitigated pected Reductions in Toxicity, Mobility and Volume pe and Quantity of Materials Remaining After Implementation gree to which the Remedy Reduces Principal Threats
rt-Term Effectiveness otection of Community during Remedial Actions vironmental Impacts of Remedial Actions ration of Remedial Actions
lementability ility to Construct and Operate the Alternative iability of the Alternative ordination with Other Stakeholders and Agencies pacity and Availability of Equipment and Specialists
t pital Costs ng-Term O&M Costs
health and the environment. The actions of excavating and dredgin impacted soils/sediment and consolidating these materials within O (delta and upland) CDF will partially cover the greatest thickness of native sediment and reduce the footprint of impacted materials acr the Site. The complimentary actions of remedial capping and place of an ENR thin cover will eliminate direct human health exposure pathways and control the risk to ecological receptors.
Execution of Alternative 6 will address regulatory requirements by achieving Upland RAOs and Estuary SMGs. The portion of the CDF residing in the OU-M delta extends along the Spit of Land eastward beyond the OHWL. The open water element north of the CDF creat additional layers of permitting and compliance with ARARs will be m complicated in comparison to Alternatives 4 and 7.
The combination of removal, consolidation and capping of impacted and sediment will effectively mitigate residual risk by eliminating hu health and ecological exposure pathways in the FS areas of concern remedy is permanent, but will require long-term monitoring and O& maintain effectiveness of engineering controls. Institutional contro layered over engineering controls will address the future threat of disturbance to protective measures associated with this remedy. Fu storm water conveyance will generally follow the current Unnamed alignment and discharge to the shallow sheltered bay created north the CDF. This alignment, in tandem with storm water retention and ponding components within OU-I, provides the lowest risk option fo managing storm water in the future consolidation/capping areas. Alternative 6 will be effective in reducing the overall risk posed by C present in the Upland and Estuary areas of the Site. This alternative utilizes industry-proven methods for removal, consolidation and ca of impacted soil and sediment. The volume of impacted material w reduced through off-site disposal of characteristic hazardous lead-impacted soil from OU-Q. However, the future mobility of COCs wi eliminated through implementation of proposed engineering contro Implementation of Alternative 6 is not anticipated to have a signific adverse effect on the community or environment while constructio underway. Construction-related traffic will be moderate and proper protective measures will be implemented to eliminate exposure ris the community. Best management practices will be implemented d construction to minimize environmental impacts. The duration of Alternative 6 is consistent with Alternatives 4 and 8 and is expected encompass a term of two years. Alternative 6 is implementable and will provide a reliable remedy to address risks posed by COCs present in the Upland and Estuary area the Site. The technology associated with this alternative is proven a there are no perceived capacity or availability issues with earth mov and dredging contractors who will perform the work. To reduce ha routes and consolidate finer grained industrial sediment close to th of original deposition, dredge material from the OU-M delta, the Unnamed Creek delta and the Wire Mill delta will be placed within comparatively narrow CDF along the Spit of Land. Consolidation of materials within a restricted foot-print will create potential sight-lin impairments with a peak height of 29 feet above the estuary. Load soft sediment and long term berm/slope stability are unique design construction challenges for this structure. Material derived from sh storm water-related improvements in OU-I will be contained within small valley-fill CDF south of OU-J. Alternative 6 is comparatively higher in cost than Alternatives 4 and because of a larger OU-M delta CDF with more significant berms an material handling requirements, but less than Alternative 7 and
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rall Protection of Human Health and the Environment man Health Protection
Mitigate the potential for direct contact with and/or incidental ingestion of impacted soils and sediment. Addresses potential recreational and trespass user risks.
vironmental Protection Reduce the potential for unacceptable risk to ecological receptors.
mpliance with Regulatory Requirements (ARARs) mpliance with Applicable Regulatory Guidance x Meets the regulatory requirements of governing agencies.
mpliance with ARARs x Actions are permit-able by stakeholder agencies.
g-Term Effectiveness and Permanence agnitude of Residual Risk x Remedy addresses residual risk to human health and the
environment. iability of Controls x Remedy is permanent and effective in the long-term.
uction of Toxicity and Mobility (Overall Risk) ocess Used and Materials Mitigated pected Reductions in Toxicity, Mobility and Volume pe and Quantity of Materials Remaining After Implementation gree to which the Remedy Reduces Principal Threats
rt-Term Effectiveness otection of Community during Remedial Actions vironmental Impacts of Remedial Actions ration of Remedial Actions
lementability ility to Construct and Operate the Technology iability of the Technology ordination with Other Stakeholders and Agencies pacity and Availability of Equipment and Specialists
Implementation of Alternative 7 is anticipated to be protective of h health and the environment. The actions of excavating and dredgin impacted soils/sediment and consolidating these materials within t Unnamed Creek corridor will reduce the footprint of impacted mate across the Site. The complimentary actions of remedial capping and placement of an ENR thin cover will eliminate direct human health exposure pathways and control the risk to ecological receptors.
Implementation of Alternative 7 will address regulatory requiremen achieving Upland RAOs and Estuary SMGs. This alternative simplifie permitting and compliance with ARARs by eliminating placement of east of the railway tracks.
The combination of removal, consolidation and capping of impacted and sediment will effectively mitigate residual risk by eliminating hu health and ecological exposure pathways in the FS areas of concern remedy is permanent, but will require long-term monitoring and O& maintain effectiveness of engineering controls. The level of effort associated with long-term O&M is anticipated to be higher compara to other alternatives as this alternative involves construction of thre challenging CDFs. Institutional controls layered over engineering co will address the future threat of disturbance to protective measure associated with this remedy. Future storm water conveyance prese the greatest challenge and risk among the alternatives advancing to detailed analysis. Consolidation of impacted media within the Unna Creek corridor will eliminate storm water retention and ponding wi OU-I and create a constricted channel for managing peak flows. Enhanced armoring of the creek channel will be necessary to mitiga berm and slope failure risks. Enhanced stabilization of CDF berms a the Unnamed Creek stream channel will be necessary to prevent CD berm and slope failure issues. Alternative 7 will be effective in reducing the overall risk posed by C present in the Upland and Estuary areas of the Site. This alternative utilizes industry-proven methods for removal, consolidation and ca of impacted soil and sediment. The volume of impacted material w reduced through off-site disposal of characteristic hazardous lead-impacted soil from OU-Q. However, the future mobility of COCs wi eliminated through implementation of proposed engineering contro Implementation of Alternative 7 is not anticipated to have a signific adverse effect on the community or environment while constructio underway. However, this alternative presents the greatest challeng temporary storm water management during construction due to extensive filling and construction activity within the Unnamed Cree corridor. Construction-related traffic will be moderate and proper protective measures will be implemented to eliminate exposure ris the community. Best management practices will be implemented d construction to minimize environmental impacts. The duration of Alternative 7 is the longest among the alternatives advancing to det analysis and is expected to encompass a term of three years. Alternative 7, while the most challenging, is implementable and wil provide a reliable remedy to address risks posed by COIs present in Upland and Estuary areas of the Site. The technology associated wi alternative is proven and there are no perceived capacity or availab issues with earth moving and dredging contractors who will perform work. Alternative 7 will entail consolidation of all removed soil and sediment into a CDF located west of the railway tracks. Consolidati these materials within the space constraints of Unnamed Creek cor results in three high CDF structures with peak heights ranging from feet above grade (within the OU-I area to 29 feet above grade (with
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man Health Protection Mitigate the potential for direct contact with and/or incidental ingestion of impacted soils and sediment. Addresses potential recreational and trespass user risks.
vironmental Protection Reduce the potential for unacceptable risk to ecological receptors.
mpliance with Regulatory Requirements (ARARs) mpliance with Applicable Regulatory Guidance x Meets the regulatory requirements of governing agencies.
mpliance with ARARs x Actions are permit-able by stakeholder agencies
g-Term Effectiveness and Permanence agnitude of Residual Risk x Remedy addresses residual risk to human health and the
environment. iability of Controls x Remedy is permanent and effective in the long-term.
uction of Toxicity and Mobility (Overall Risk) ocess Used and Materials Mitigated pected Reductions in Toxicity, Mobility and Volume pe and Quantity of Materials Remaining After Implementation gree to which the Remedy Reduces Principal Threats
rt-Term Effectiveness otection of Community during Remedial Actions vironmental Impacts of Remedial Actions ration of Remedial Actions
lementability ility to Construct and Operate the Alternative iability of the Alternative ordination with Other Stakeholders and Agencies pacity and Availability of Equipment and Specialists
t pital Costs
health and the environment. Similar to other alternatives, the actio excavating and dredging impacted soils/sediment and consolidating materials within CDF structures will partially cover residual non-nat sediment and reduce the footprint of impacted materials across the The complimentary actions of remedial capping and placement of a thin cover will eliminate direct human health exposure pathways an control the risk to ecological receptors.
Execution of Alternative 8 will address regulatory requirements by achieving Upland RAOs and Estuary SMGs. To create a shallow shel bay habitat betterment in the OU-M delta, non-native sediment excavated during this process will be consolidated within a low prof single source CDF extending along the Spit of Land eastward beyon OHWL. This open water element creates additional layers of permi and compliance with ARARs in comparison to Alternatives 4 and 7. The combination of removal, consolidation and capping of impacted and sediment will effectively mitigate residual risk by eliminating hu health and ecological exposure pathways in the FS areas of concern remedy is permanent, but will require long-term monitoring and O& maintain effectiveness of engineering controls. The level of effort associated with long-term O&M for the three CDFs is anticipated to similar to Alternative 6 but less than Alternative 7. Institutional con layered over engineering controls will address the future threat of disturbance to protective measures associated with this remedy. Fu storm water conveyance will generally follow the current Unnamed alignment and discharge to the shallow sheltered bay created north the CDF. This alignment, in tandem with storm water retention and ponding components within OU-I, provides the lowest risk option fo managing storm water in the future consolidation/capping areas. Alternative 8 will be effective in reducing the overall risk posed by C present in the Upland and Estuary areas of the Site. This alternative utilizes industry-proven methods for removal, consolidation and ca of impacted soil and sediment. The volume of impacted material w reduced through off-site disposal of characteristic hazardous lead-impacted soil from OU-Q. However, the future mobility of COCs wi eliminated through implementation of proposed engineering contro Implementation of Alternative 8 is not anticipated to have a signific adverse effect on the community or environment while constructio underway. Construction-related traffic will be moderate and proper protective measures will be implemented to eliminate exposure ris the community. Best management practices will be implemented d construction to minimize environmental impacts. The duration of Alternative 8 is consistent with Alternatives 4 and 6 and is expected encompass a term of two years. Alternative 8 is implementable and will provide a reliable remedy to address risks posed by COIs present in the Upland and Estuary area the Site. The technology associated with this alternative is proven a there are no perceived capacity or availability issues with earth mov and dredging contractors who will perform the work. Consolidation non-native sediment will largely be proximal to its source area, imp construction efficiencies and simplifying staging. Material derived f the OU-M delta shallow sheltered bay removal area will be containe the same area within the delta sediment CDF. Material derived from estuary dredge areas, as well as OU-P and Q and the Unnamed Pon be contained within the OU-M upland area CDF. Material derived f shallow storm water-related improvements in OU-I will be containe within a small valley-fill CDF south of OU-J. Alternative 8 is comparatively higher in cost than Alternative 4, but exceeded by Alternatives 6, 7, and 12 among the options advancing
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man Health Protection Mitigate the potential for direct contact with and/or incidental ingestion of impacted soils and sediment. Addresses potential recreational and trespass user risks.
vironmental Protection Reduce the potential for unacceptable risk to ecological receptors.
mpliance with Regulatory Requirements (ARARs) mpliance with Applicable Regulatory Guidance x Meets the regulatory requirements of governing agencies.
mpliance with ARARs x Actions are permit-able by stakeholder agencies
g-Term Effectiveness and Permanence agnitude of Residual Risk x Remedy addresses residual risk to human health and
the environment. iability of Controls x Remedy is permanent and effective in the long-term.
uction of Toxicity and Mobility (Overall Risk) ocess Used and Materials Mitigated pected Reductions in Toxicity, Mobility and Volume pe and Quantity of Materials Remaining After lementation gree to which the Remedy Reduces Principal Threats
rt-Term Effectiveness otection of Community during Remedial Actions vironmental Impacts of Remedial Actions ration of Remedial Actions
lementability ility to Construct and Operate the Alternative iability of the Alternative ordination with Other Stakeholders and Agencies pacity and Availability of Equipment and Specialists
and the environment. Similar to other alternatives, the actions of excavating dredging impacted soils/sediment and consolidating these materials within C structures will partially cover residual non-native sediment and reduce the fo of impacted materials across the Site. The complimentary actions of remedi capping and placement of an ENR thin cover will eliminate direct human hea exposure pathways and control the risk to ecological receptors.
Execution of Alternative 12 will address regulatory requirements by achievin Upland RAOs and Estuary SMGs. To create an open water bay habitat better the OU-M delta, non-native sediment excavated during this process will be r from the delta and placed in several upland CDFs. This alternative simplifies permitting by eliminating placement of a CDF east of the railway tracks but r third CDF location that requires other permitting considerations.
The combination of removal, consolidation and capping of impacted soil and sediment will effectively mitigate residual risk by eliminating human health a ecological exposure pathways in the FS areas of concern. The remedy is perm but will require long-term monitoring and O&M to maintain effectiveness of engineering controls. The level of effort associated with long-term O&M for three CDFs is anticipated to be more than Alternatives 6 and 8 because the t is located a significant distance away from the other two CDFs. However, the effort is anticipated to be less than Alternative 7. Institutional controls layere engineering controls will address the future threat of disturbance to protect measures associated with this remedy. Future storm water conveyance will g follow the current Unnamed Creek alignment and discharge to the open wat created north of the spit. This alignment, in tandem with storm water reten ponding components within OU-I, provides the lowest risk option for manag storm water in the future consolidation/capping areas. Alternative 12 will be effective in reducing the overall risk posed by COIs pre the Upland and Estuary areas of the Site. This alternative utilizes industry-pr methods for removal, consolidation and capping of impacted soil and sedime volume of impacted material will be reduced through off-site disposal of characteristic hazardous lead-impacted soil from OU-Q. However, the future mobility of COCs will be eliminated through implementation of proposed engineering controls. Implementation of Alternative 12 is not anticipated to have a significant adv effect on the community or environment while construction is underway. Construction-related traffic will be moderate but likely less than the other op advancing to detailed analysis because material generated from excavation o borrow site CDF will be utilized for earthwork, reducing the volume of impor material required. However, more on-site transportation will be required be the haul distance to the CDFs. Proper protective measures will be implement eliminate exposure risk to the community. Best management practices will b implemented during construction to minimize environmental impacts. Becau the additional volume removed from the OU-M Delta, construction of tall be the OU-M Upland CDF, and excavation of the Borrow Site CDF, the construct duration is expected to encompass a term of three years, which is longer tha Alternatives 4, 6, and 8 and consistent with Alternative 7. Alternative 12 is implementable and will provide a reliable remedy to addres posed by COIs present in the Upland and Estuary areas of the Site. The techn associated with this alternative is proven and there are no perceived capacit availability issues with earth moving and dredging contractors who will perfo work. Although consolidation of non-native material will be proximal to its s area where feasible, on average it will require greater travel distances than Alternative 8, reducing construction efficiencies and complicating staging. T Upland CDF will be filled with material generated from the Unnamed Creek d area and the open water bay removal area. The berms at the OU-M Upland C be much higher than in Alternatives 4, 6, and 8, and similar to those in Altern Additionally, because of the limited capacity of the OU-M Upland CDF, a sign volume of material from the open water bay removal area will be transporte
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ŽŵƉůŝĂŶƚ
i
0
n Co
sts
-M D
elta
d
Tran
spor
t - S
ubaq
euou
s
d Tr
ansp
ort -
Dry
Suba
qeuo
us
nd S
hoal
Con
stru
ctio
n - D
ry
Stab
iliza
tion
ratio
ns A
rea
n an
d Tr
ansp
ort
er F
eatu
res
nd R
esto
ratio
n
on, C
appi
ng, a
nd O
pera
tion
Tran
spor
t, an
d Re
stor
atio
n
agem
ent a
nd T
reat
men
t on
and
Dem
obili
zatio
n
atio
n
and
Adm
inist
ratio
n Q
A, a
nd R
epor
ting
Prep
arat
ion,
Mob
iliza
tion,
and
Dem
obili
zatio
n r P
repa
ratio
n, M
obili
zatio
n, D
emob
iliza
tion
al
Alte
rnat
ive
4 $2
1,40
0,00
0 $4
,790
,000
$3,0
80,0
00
$11,
200,
000
$2,3
10,0
00
$70,
000
$10,
000,
000
$910
,000
$5,8
50,0
00
$3,2
70,0
00
$9,1
00,0
00
$9,1
50,0
00
$5,0
00,0
00
$5,0
00,0
00
$2,6
00,0
00
$1,1
10,0
00
$1,4
90,0
00
$6,2
00,0
00
$6,1
50,0
00
$6,9
00,0
00
$6,8
60,0
00
$61,
000,
000
Alte
rnat
ive
6 $2
6,00
0,00
0 $4
,790
,000
$5,0
80,0
00
$10,
830,
000
$5,2
50,0
00
$70,
000
$5,5
00,0
00
$750
,000
$2,0
00,0
00
$2,7
70,0
00
$14,
300,
000
$14,
290,
000
$5,0
00,0
00
$5,0
00,0
00
$3,4
00,0
00
$1,1
10,0
00
$2,2
90,0
00
$6,8
00,0
00
$6,8
40,0
00
$7,2
00,0
00
$7,1
60,0
00
$68,
000,
000
Alte
rnat
ive
7 $2
9,80
0,00
0 $4
,790
,000
$5,5
90,0
00
$10,
830,
000
$8,4
80,0
00
$70,
000
$10,
700,
000
$500
,000
$8,6
80,0
00
$1,5
60,0
00
$16,
000,
000
$15,
980,
000
$5,0
00,0
00
$5,0
00,0
00
$5,2
40,0
00
$1,1
10,0
00
$4,1
30,0
00
$8,4
00,0
00
$8,4
10,0
00
$8,5
00,0
00
$8,5
00,0
00
$84,
000,
000
Alte
rnat
ive
8 $2
6,10
0,00
0 $4
,790
,000
$5,0
80,0
00
$10,
830,
000
$5,3
00,0
00
$70,
000
$5,1
00,0
00
$750
,000
$2,0
00,0
00
$2,3
80,0
00
$12,
500,
000
$12,
480,
000
$5,0
00,0
00
$5,0
00,0
00
$3,6
50,0
00
$1,1
10,0
00
$2,5
40,0
00
$6,6
00,0
00
$6,5
80,0
00
$6,6
00,0
00
$6,6
00,0
00
$66,
000,
000
Alte
rnat
iv
$31,
100,
0 $4
,790
,00
$6,5
70,0
0
$10,
830,
0
$8,8
70,0
0
$70,
000
$5,1
00,0
$7
50,0
0
$2,0
00,0
0
$2,3
80,0
0
$16,
300,
0 $1
6,27
0,0
$4,8
00,0
$4
,830
,00
$4,1
80,0
$1
,110
,00
$3,0
70,0
0
$7,8
00,0
$7
,750
,00
$7,5
00,0
$7
,550
,00
$77,
000,
0
nd M
aint
enan
ce -
30 Y
ear L
ife C
ycle
Cos
ts R
ange
al ions
Are
a Su
btot
al
Alte
rnat
ive
4 Al
tern
ativ
e 6
Alte
rnat
ive
7 Al
tern
ativ
e 8
Alte
rnat
iv
Low
-
High
$1
,400
,000
-
$3,3
00,0
00
$6,2
00,0
00
-$9
,600
,000
$7
,600
,000
-
$12,
900,
000
Low
-
High
$1
,400
,000
-
$3,3
00,0
00
$3,4
00,0
00
-$7
,000
,000
$4
,800
,000
-
$10,
300,
000
Low
-
High
$1
,600
,000
-
$3,6
00,0
00
$9,3
00,0
00
-$1
3,40
0,00
0 $1
0,90
0,00
0 -
$17,
000,
000
Low
-
High
$1
,600
,000
-
$3,6
00,0
00
$4,1
00,0
00
-$8
,000
,000
$5
,700
,000
-
$11,
600,
000
Low
-
$1,8
00,0
00
-$4
,200
,000
-
$6,0
00,0
00
-$
Ap
prox
imat
eU
. S. S
teel
Ope
ratio
ns A
rea
Spiri
t Lak
e
Wire
Mill
Del
ta
Unn
amed
Cre
ek D
elta
S
pirit
Isla
nd
Unnam
edC
reek
Railway
Wire
Mill
Pon
d
Mor
gan
Park
St. L
ouis
Riv
er
St.L
ouisRiverChannel
ESOTA IN
